Author: "Jaa A" / Topic: hep-ex - Searchworks@Jio Institute Digital Library Search Results

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118 results on '"Jaa A"'

1. Measurements of Higgs bosons decaying to bottom quarks from vector boson fusion production with the ATLAS experiment at √s=13TeV

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmad, A, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Akbiyik, M, Åkesson, TPA, Akilli, E, Akimov, AV, Al Khoury, K, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Ali, S, Aliev, M, Alimonti, G, Allaire, C, Allbrooke, BMM, Allport, PP, Aloisio, A, Alonso, F, Alpigiani, C, Camelia, EA, Estevez, MA, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, Anastopoulos, C, Andari, N, Andeen, T, Anders, JK, Andrean, SY, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Aparo, MA, Bella, LA, Aranzabal, N, Ferraz, VA, Pereira, RA, Arcangeletti, C, Arce, ATH, and Arguin, JF
Subjects: hep-ex, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Quantum Physics
Abstract: The paper presents a measurement of the Standard Model Higgs Boson decaying to b-quark pairs in the vector boson fusion (VBF) production mode. A sample corresponding to 126 fb - 1 of s=13TeV proton–proton collision data, collected with the ATLAS experiment at the Large Hadron Collider, is analyzed utilizing an adversarial neural network for event classification. The signal strength, defined as the ratio of the measured signal yield to that predicted by the Standard Model for VBF Higgs production, is measured to be 0.95-0.36+0.38 , corresponding to an observed (expected) significance of 2.6 (2.8) standard deviations from the background only hypothesis. The results are additionally combined with an analysis of Higgs bosons decaying to b-quarks, produced via VBF in association with a photon.
Published: 2021

2. Optimisation of large-radius jet reconstruction for the ATLAS detector in 13 TeV proton–proton collisions

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmad, A, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Akbiyik, M, Åkesson, TPA, Akilli, E, Akimov, AV, Al Khoury, K, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Ali, S, Aliev, M, Alimonti, G, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, F, Alpigiani, C, Camelia, EA, Estevez, MA, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, JK, Andrean, SY, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Aparo, MA, Bella, LA, Aranzabal, N, Ferraz, VA, and Pereira, RA
Subjects: hep-ex, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Quantum Physics
Abstract: Jet substructure has provided new opportunities for searches and measurements at the LHC, and has seen continuous development since the optimization of the large-radius jet definition used by ATLAS was performed during Run 1. A range of new inputs to jet reconstruction, pile-up mitigation techniques and jet grooming algorithms motivate an optimisation of large-radius jet reconstruction for ATLAS. In this paper, this optimisation procedure is presented, and the performance of a wide range of large-radius jet definitions is compared. The relative performance of these jet definitions is assessed using metrics such as their pileup stability, ability to identify hadronically decaying W bosons and top quarks with large transverse momenta. A new type of jet input object, called a ‘unified flow object’ is introduced which combines calorimeter- and inner-detector-based signals in order to achieve optimal performance across a wide kinematic range. Large-radius jet definitions are identified which significantly improve on the current ATLAS baseline definition, and their modelling is studied using pp collisions recorded by the ATLAS detector at s=13TeV during 2017.
Published: 2021

3. Search for pair production of scalar leptoquarks decaying into first- or second-generation leptons and top quarks in proton–proton collisions at √s = 13 TeV with the ATLAS detector

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmad, A, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Akbiyik, M, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Ali, S, Aliev, M, Alimonti, G, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, F, Alpigiani, C, Camelia, EA, Estevez, MA, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, JK, Andrean, SY, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Aparo, MA, Bella, LA, Aranzabal, N, Ferraz, VA, Pereira, RA, and Arcangeletti, C
Subjects: hep-ex, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Quantum Physics
Abstract: A search for pair production of scalar leptoquarks, each decaying into either an electron or a muon and a top quark, is presented. This is the first leptoquark search using ATLAS data to investigate top-philic cross-generational couplings that could provide explanations for recently observed anomalies in B meson decays. This analysis targets high leptoquark masses which cause the decay products of each resultant top quark to be contained within a single high-pT large-radius jet. The full Run 2 dataset is exploited, consisting of 139fb-1 of data collected from proton–proton collisions at s=13TeV from 2015 to 2018 with the ATLAS detector at the CERN Large Hadron Collider. In the absence of any significant deviation from the background expectation, lower limits on the leptoquark masses are set at 1480GeV and 1470GeV for the electron and muon channel, respectively.
Published: 2021

4. Measurement of the CP-violating phase ϕs in Bs0→J/ψϕ decays in ATLAS at 13 TeV

Author: Aad, G, Abbott, B, Abbott, DC, Abdinov, O, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adachi, S, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexandre, D, Alexopoulos, T, Alfonsi, A, Alhroob, M, Ali, B, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Estevez, MA, Piqueras, DÁ, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, CF, Anders, JK, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Bella, LA, Arabidze, G, Araque, JP, and Ferraz, VA
Subjects: hep-ex, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Quantum Physics
Abstract: A measurement of the Bs0→J/ψϕ decay parameters using 80.5fb-1 of integrated luminosity collected with the ATLAS detector from 13 Te proton–proton collisions at the LHC is presented. The measured parameters include the CP-violating phase ϕs, the width difference Δ Γ s between the Bs0 meson mass eigenstates and the average decay width Γ s. The values measured for the physical parameters are combined with those from 19.2fb-1 of 7 and 8 Te data, leading to the following: ϕs=-0.087±0.036(stat.)±0.021(syst.)radΔΓs=0.0657±0.0043(stat.)±0.0037(syst.)ps-1Γs=0.6703±0.0014(stat.)±0.0018(syst.)ps-1Results for ϕs and Δ Γ s are also presented as 68% confidence level contours in the ϕs–Δ Γ s plane. Furthermore the transversity amplitudes and corresponding strong phases are measured. ϕs and Δ Γ s measurements are in agreement with the Standard Model predictions.
Published: 2021

5. Search for type-III seesaw heavy leptons in dilepton final states in pp collisions at √s=13TeV with the ATLAS detector

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmad, A, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Akbiyik, M, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Ali, S, Aliev, M, Alimonti, G, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, F, Alpigiani, C, Camelia, EA, Estevez, MA, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, JK, Andrean, SY, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Aparo, MA, Bella, LA, Aranzabal, N, Ferraz, VA, and Pereira, RA
Subjects: hep-ex, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Quantum Physics, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: A search for the pair production of heavy leptons as predicted by the type-III seesaw mechanism is presented. The search uses proton–proton collision data at a centre-of-mass energy of 13 TeV, corresponding to 139fb-1 of integrated luminosity recorded by the ATLAS detector during Run 2 of the Large Hadron Collider. The analysis focuses on the final state with two light leptons (electrons or muons) of different flavour and charge combinations, with at least two jets and large missing transverse momentum. No significant excess over the Standard Model expectation is observed. The results are translated into exclusion limits on heavy-lepton masses, and the observed lower limit on the mass of the type-III seesaw heavy leptons is 790 GeV at 95% confidence level.
Published: 2021

6. Measurements of WH and ZH production in the H→ bb¯ decay channel in pp collisions at 13Te with the ATLAS detector

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmad, A, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Akbiyik, M, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Ali, S, Aliev, M, Alimonti, G, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, F, Alpigiani, C, Camelia, EA, Estevez, MA, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, JK, Andrean, SY, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Aparo, MA, Bella, LA, Aranzabal, N, Ferraz, VA, and Pereira, RA
Subjects: hep-ex, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Quantum Physics, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: Measurements of the Standard Model Higgs boson decaying into a bb¯ pair and produced in association with a W or Z boson decaying into leptons, using proton–proton collision data collected between 2015 and 2018 by the ATLAS detector, are presented. The measurements use collisions produced by the Large Hadron Collider at a centre-of-mass energy of s=13Te, corresponding to an integrated luminosity of 139fb-1. The production of a Higgs boson in association with a W or Z boson is established with observed (expected) significances of 4.0 (4.1) and 5.3 (5.1) standard deviations, respectively. Cross-sections of associated production of a Higgs boson decaying into bottom quark pairs with an electroweak gauge boson, W or Z, decaying into leptons are measured as a function of the gauge boson transverse momentum in kinematic fiducial volumes. The cross-section measurements are all consistent with the Standard Model expectations, and the total uncertainties vary from 30% in the high gauge boson transverse momentum regions to 85% in the low regions. Limits are subsequently set on the parameters of an effective Lagrangian sensitive to modifications of the WH and ZH processes as well as the Higgs boson decay into bb¯.
Published: 2021

7. Search for phenomena beyond the Standard Model in events with large b-jet multiplicity using the ATLAS detector at the LHC

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmad, A, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Akbiyik, M, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Ali, S, Aliev, M, Alimonti, G, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, F, Alpigiani, C, Camelia, EA, Estevez, MA, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, JK, Andrean, SY, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Aparo, MA, Bella, LA, Aranzabal, N, Ferraz, VA, and Pereira, RA
Subjects: hep-ex, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Quantum Physics, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: A search is presented for new phenomena in events characterised by high jet multiplicity, no leptons (electrons or muons), and four or more jets originating from the fragmentation of b-quarks (b-jets). The search uses 139fb-1 of s = 13 TeV proton–proton collision data collected by the ATLAS experiment at the Large Hadron Collider during Run 2. The dominant Standard Model background originates from multijet production and is estimated using a data-driven technique based on an extrapolation from events with low b-jet multiplicity to the high b-jet multiplicities used in the search. No significant excess over the Standard Model expectation is observed and 95% confidence-level limits that constrain simplified models of R-parity-violating supersymmetry are determined. The exclusion limits reach 950 GeV in top-squark mass in the models considered.
Published: 2021

8. Search for Higgs boson decays into two new low-mass spin-0 particles in the 4b channel with the ATLAS detector using pp collisions at √s = 13 TeV

Author: Aad, G, Abbott, B, Abbott, DC, Abdinov, O, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adachi, S, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Al Khoury, K, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexandre, D, Alexopoulos, T, Alfonsi, A, Alhroob, M, Ali, B, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Estevez, MA, Piqueras, DÁ, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Dos Santos, SPA, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, CF, Anders, JK, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Bella, LA, Arabidze, G, Araque, JP, and Ferraz, VA
Subjects: hep-ex
Abstract: This paper describes a search for beyond the Standard Model decays of the Higgs boson into a pair of new spin-0 particles subsequently decaying into b-quark pairs, H → aa → (bb¯)(bb¯), using protonproton collision data collected by the ATLAS detector at the Large Hadron Collider at center-of-mass energy √s = 13 TeV. This search focuses on the range 15 GeV ≤ ma ≤ 30 GeV, where the decay products are collimated; it is complementary to a previous search in the same final state targeting the range 20 GeV ≤ ma ≤ 60 GeV, where the decay products are well separated. A novel strategy for the identification of the a → bb¯ decays is deployed to enhance the efficiency for topologies with small separation angles. The search is performed with 36 fb-1 of integrated luminosity collected in 2015 and 2016 and sets upper limits on the production cross section of H → aa → (bb¯)(bb¯), where the Higgs boson is produced in association with a Z boson.
Published: 2020

9. Alignment of the ATLAS Inner Detector in Run 2

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmad, A, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Akbiyik, M, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Ali, S, Aliev, M, Alimonti, G, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, F, Alpigiani, C, Camelia, EA, Estevez, MA, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, JK, Andrean, SY, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Aparo, MA, Bella, LA, Aranzabal, N, Ferraz, VA, and Pereira, RA
Subjects: hep-ex, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Quantum Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: The performance of the ATLAS Inner Detector alignment has been studied using pp collision data at s=13TeV collected by the ATLAS experiment during Run 2 (2015–2018) of the Large Hadron Collider (LHC). The goal of the detector alignment is to determine the detector geometry as accurately as possible and correct for time-dependent movements. The Inner Detector alignment is based on the minimization of track-hit residuals in a sequence of hierarchical levels, from global mechanical assembly structures to local sensors. Subsequent levels have increasing numbers of degrees of freedom; in total there are almost 750,000. The alignment determines detector geometry on both short and long timescales, where short timescales describe movements within an LHC fill. The performance and possible track parameter biases originating from systematic detector deformations are evaluated. Momentum biases are studied using resonances decaying to muons or to electrons. The residual sagitta bias and momentum scale bias after alignment are reduced to less than ∼0.1TeV-1 and 0.9 × 10 - 3, respectively. Impact parameter biases are also evaluated using tracks within jets.
Published: 2020

10. Search for heavy diboson resonances in semileptonic final states in pp collisions at √s=13 TeV with the ATLAS detector

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmad, A, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Ali, S, Aliev, M, Alimonti, G, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, F, Alpigiani, C, Camelia, EA, Estevez, MA, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, JK, Andrean, SY, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Aparo, MA, Bella, LA, Aranzabal, N, Ferraz, VA, Pereira, RA, and Arcangeletti, C
Subjects: hep-ex, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Quantum Physics, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: This paper reports on a search for heavy resonances decaying into WW, ZZ or WZ using proton–proton collision data at a centre-of-mass energy of s=13 TeV. The data, corresponding to an integrated luminosity of 139 fb 1, were recorded with the ATLAS detector from 2015 to 2018 at the Large Hadron Collider. The search is performed for final states in which one W or Z boson decays leptonically, and the other W boson or Z boson decays hadronically. The data are found to be described well by expected backgrounds. Upper bounds on the production cross sections of heavy scalar, vector or tensor resonances are derived in the mass range 300–5000 GeV within the context of Standard Model extensions with warped extra dimensions or including a heavy vector triplet. Production through gluon–gluon fusion, Drell–Yan or vector-boson fusion are considered, depending on the assumed model.
Published: 2020

11. Search for top squarks in events with a Higgs or Z boson using 139 fb - 1 of pp collision data at √s=13 TeV with the ATLAS detector

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmad, A, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Akbiyik, M, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Ali, S, Aliev, M, Alimonti, G, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, F, Alpigiani, C, Camelia, EA, Estevez, MA, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, JK, Andrean, SY, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Aparo, MA, Bella, LA, Barrio, NA, Ferraz, VA, and Pereira, RA
Subjects: hep-ex, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Quantum Physics
Abstract: This paper presents a search for direct top squark pair production in events with missing transverse momentum plus either a pair of jets consistent with Standard Model Higgs boson decay into b-quarks or a same-flavour opposite-sign dilepton pair with an invariant mass consistent with a Z boson. The analysis is performed using the proton–proton collision data at s=13 TeV collected with the ATLAS detector during the LHC Run-2, corresponding to an integrated luminosity of 139 fb- 1. No excess is observed in the data above the Standard Model predictions. The results are interpreted in simplified models featuring direct production of pairs of either the lighter top squark (t~ 1) or the heavier top squark (t~ 2), excluding at 95% confidence level t~ 1 and t~ 2 masses up to about 1220 and 875 GeV, respectively.
Published: 2020

12. Evidence for tt¯ tt¯ production in the multilepton final state in proton–proton collisions at √s=13 TeV with the ATLAS detector

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmad, A, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Akbiyik, M, Åkesson, TPA, Akilli, E, Akimov, AV, Al Khoury, K, Alberghi, GL, Albert, J, Alconada Verzini, MJ, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Ali, S, Aliev, M, Alimonti, G, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, F, Alpigiani, C, Camelia, EA, Estevez, MA, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, JK, Andrean, SY, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Aparo, MA, Bella, LA, Aranzabal, N, Ferraz, VA, and Pereira, RA
Subjects: hep-ex, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Quantum Physics
Abstract: A search is presented for four-top-quark production using an integrated luminosity of 139 fb- 1 of proton–proton collision data at a centre-of-mass energy of 13TeV collected by the ATLAS detector at the LHC. Events are selected if they contain a same-sign lepton pair or at least three leptons (electrons or muons). Jet multiplicity, jet flavour and event kinematics are used to separate signal from the background through a multivariate discriminant, and dedicated control regions are used to constrain the dominant backgrounds. The four-top-quark production cross section is measured to be 24-6+7 fb. This corresponds to an observed (expected) significance with respect to the background-only hypothesis of 4.3 (2.4) standard deviations and provides evidence for this process.
Published: 2020

13. Higgs boson production cross-section measurements and their EFT interpretation in the 4 ℓ decay channel at √s= 13 TeV with the ATLAS detector

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmad, A, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Ali, S, Aliev, M, Alimonti, G, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, F, Alpigiani, C, Camelia, EA, Estevez, MA, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, JK, Andrean, SY, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Aparo, MA, Bella, LA, Barrio, NA, Ferraz, VA, Pereira, RA, and Arcangeletti, C
Subjects: hep-ex, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Quantum Physics, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: Higgs boson properties are studied in the four-lepton decay channel (where lepton = e, μ) using 139 fb - 1 of proton–proton collision data recorded at s=13 TeV by the ATLAS experiment at the Large Hadron Collider. The inclusive cross-section times branching ratio for H→ ZZ∗ decay is measured to be 1.34 ± 0.12 pb for a Higgs boson with absolute rapidity below 2.5, in good agreement with the Standard Model prediction of 1.33 ± 0.08 pb. Cross-sections times branching ratio are measured for the main Higgs boson production modes in several exclusive phase-space regions. The measurements are interpreted in terms of coupling modifiers and of the tensor structure of Higgs boson interactions using an effective field theory approach. Exclusion limits are set on the CP-even and CP-odd ‘beyond the Standard Model’ couplings of the Higgs boson to vector bosons, gluons and top quarks.
Published: 2020

14. Measurements of the Higgs boson inclusive and differential fiducial cross sections in the 4 ℓ decay channel at √s = 13 TeV

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmad, A, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Ali, S, Aliev, M, Alimonti, G, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, F, Alpigiani, C, Camelia, EA, Estevez, MA, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, JK, Andrean, SY, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Aparo, MA, Bella, LA, Barrio, NA, Ferraz, VA, Pereira, RA, and Arcangeletti, C
Subjects: hep-ex, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Quantum Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: Inclusive and differential fiducial cross sections of the Higgs boson are measured in the H→ ZZ∗→ 4 ℓ (ℓ= e, μ) decay channel. The results are based on proton−proton collision data produced at the Large Hadron Collider at a centre-of-mass energy of 13 TeV and recorded by the ATLAS detector from 2015 to 2018, equivalent to an integrated luminosity of 139 fb - 1. The inclusive fiducial cross section for the H→ ZZ∗→ 4 ℓ process is measured to be σfid= 3.28 ± 0.32 fb, in agreement with the Standard Model prediction of σfid , SM= 3.41 ± 0.18 fb. Differential fiducial cross sections are measured for a variety of observables which are sensitive to the production and decay of the Higgs boson. All measurements are in agreement with the Standard Model predictions. The results are used to constrain anomalous Higgs boson interactions with Standard Model particles.
Published: 2020

15. Performance of the ATLAS muon triggers in Run 2

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, Abouzeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmad, A, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Ali, S, Aliev, M, Alimonti, G, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, F, Alpigiani, C, Alshehri, AA, Camelia, EA, Estevez, MA, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Dos Santos, SPA, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, CF, Anders, JK, Andrean, SY, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Aparo, MA, Bella, LA, Ferraz, VA, and Pereira, RA
Subjects: Data acquisition concepts, Data processing methods, Online farms and online filtering, Trigger concepts and systems, physics.ins-det, hep-ex, Nuclear & Particles Physics, Physical Sciences, Engineering
Abstract: The performance of the ATLAS muon trigger system is evaluated with proton-proton (pp) and heavy-ion (HI) collision data collected in Run 2 during 2015-2018 at the Large Hadron Collider. It is primarily evaluated using events containing a pair of muons from the decay of Z bosons to cover the intermediate momentum range between 26 GeV and 100 GeV. Overall, the efficiency of the single-muon triggers is about 68% in the barrel region and 85% in the endcap region. The pT range for efficiency determination is extended by using muons from decays of Jψ mesons, W bosons, and top quarks. The performance in HI collision data is measured and shows good agreement with the results obtained in pp collisions. The muon trigger shows uniform and stable performance in good agreement with the prediction of a detailed simulation. Dedicated multi-muon triggers with kinematic selections provide the backbone to beauty, quarkonia, and low-mass physics studies. The design, evolution and performance of these triggers are discussed in detail.
Published: 2020

16. Search for direct production of electroweakinos in final states with one lepton, missing transverse momentum and a Higgs boson decaying into two b-jets in pp collisions at √s=13 TeV with the ATLAS detector

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abulaiti, Y, Abreu, H, Acharya, BS, Achkar, B, Adachi, S, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexandre, D, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Aliev, M, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Estevez, MA, Piqueras, DÁ, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, CF, Anders, JK, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Bella, LA, and Arabidze, G
Subjects: hep-ex, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Quantum Physics
Abstract: The results of a search for electroweakino pair production pp→χ~1±χ~20 in which the chargino (χ~1±) decays into a W boson and the lightest neutralino (χ~10), while the heavier neutralino (χ~20) decays into the Standard Model 125 GeV Higgs boson and a second χ~10 are presented. The signal selection requires a pair of b-tagged jets consistent with those from a Higgs boson decay, and either an electron or a muon from the W boson decay, together with missing transverse momentum from the corresponding neutrino and the stable neutralinos. The analysis is based on data corresponding to 139 fb - 1 of s=13 TeV pp collisions provided by the Large Hadron Collider and recorded by the ATLAS detector. No statistically significant evidence of an excess of events above the Standard Model expectation is found. Limits are set on the direct production of the electroweakinos in simplified models, assuming pure wino cross-sections. Masses of χ~1±/χ~20 up to 740 GeV are excluded at 95% confidence level for a massless χ~10.
Published: 2020

17. Measurements of top-quark pair spin correlations in the eμ channel at √s=13 TeV using pp collisions in the ATLAS detector

Author: Aaboud, M, Aad, G, Abbott, B, Abbott, DC, Abdinov, O, Abud, AA, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Adachi, S, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Ai, X, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexandre, D, Alexopoulos, T, Alfonsi, A, Alhroob, M, Ali, B, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Alstaty, MI, Estevez, MA, Gonzalez, BA, Piqueras, DÁ, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, CF, Anders, JK, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angelozzi, I, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Bella, LA, Arabidze, G, and Araque, JP
Subjects: hep-ex, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Quantum Physics
Abstract: A measurement of observables sensitive to spin correlations in tt¯ production is presented, using 36.1 fb - 1 of pp collision data at s=13 TeV recorded with the ATLAS detector at the Large Hadron Collider. Differential cross-sections are measured in events with exactly one electron and one muon with opposite-sign electric charge as a function of the azimuthal opening angle and the absolute difference in pseudorapidity between the electron and muon candidates in the laboratory frame. The azimuthal opening angle is also measured as a function of the invariant mass of the tt¯ system. The measured differential cross-sections are compared to predictions by several NLO Monte Carlo generators and fixed-order calculations. The observed degree of spin correlation is somewhat higher than predicted by the generators used. The data are consistent with the prediction of one of the fixed-order calculations at NLO, but agree less well with higher-order predictions. Using these leptonic observables, a search is performed for pair production of supersymmetric top squarks decaying into Standard Model top quarks and light neutralinos. Top squark masses between 170 and 230 GeV are largely excluded at the 95% confidence level for kinematically allowed values of the neutralino mass.
Published: 2020

18. Measurement of the transverse momentum distribution of Drell–Yan lepton pairs in proton–proton collisions at √s=13 TeV with the ATLAS detector

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adachi, S, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Aliev, M, Alimonti, G, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, F, Alpigiani, C, Alshehri, AA, Camelia, EA, Estevez, MA, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, CF, Anders, JK, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Bella, LA, Araque, JP, Ferraz, VA, Pereira, RA, and Arcangeletti, C
Subjects: hep-ex, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Quantum Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: This paper describes precision measurements of the transverse momentum pTℓℓ (ℓ= e, μ) and of the angular variable ϕη∗ distributions of Drell–Yan lepton pairs in a mass range of 66–116 GeV. The analysis uses data from 36.1 fb- 1 of proton–proton collisions at a centre-of-mass energy of s=13TeV collected by the ATLAS experiment at the LHC in 2015 and 2016. Measurements in electron-pair and muon-pair final states are performed in the same fiducial volumes, corrected for detector effects, and combined. Compared to previous measurements in proton–proton collisions at s=7 and 8TeV, these new measurements probe perturbative QCD at a higher centre-of-mass energy with a different composition of initial states. They reach a precision of 0.2% for the normalized spectra at low values of pTℓℓ. The data are compared with different QCD predictions, where it is found that predictions based on resummation approaches can describe the full spectrum within uncertainties.
Published: 2020

19. Measurement of the tt¯ production cross-section and lepton differential distributions in eμ dilepton events from pp collisions at √s=13TeV with the ATLAS detector

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adachi, S, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Aliev, M, Alimonti, G, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Estevez, MA, Piqueras, DÁ, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, CF, Anders, JK, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Bella, LA, Araque, JP, Ferraz, VA, and Pereira, RA
Subjects: hep-ex, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Quantum Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: The inclusive top quark pair (tt¯) production cross-section σtt¯ has been measured in proton–proton collisions at s=13TeV, using 36.1 fb- 1 of data collected in 2015–2016 by the ATLAS experiment at the LHC. Using events with an opposite-charge eμ pair and b-tagged jets, the cross-section is measured to be: σtt¯=826.4±3.6(stat)±11.5(syst)±15.7(lumi)±1.9(beam)pb,where the uncertainties reflect the limited size of the data sample, experimental and theoretical systematic effects, the integrated luminosity, and the LHC beam energy, giving a total uncertainty of 2.4%. The result is consistent with theoretical QCD calculations at next-to-next-to-leading order. It is used to determine the top quark pole mass via the dependence of the predicted cross-section on mtpole, giving mtpole=173.1-2.1+2.0GeV. It is also combined with measurements at s=7TeV and s=8TeV to derive ratios and double ratios of tt¯ and Z cross-sections at different energies. The same event sample is used to measure absolute and normalised differential cross-sections as functions of single-lepton and dilepton kinematic variables, and the results are compared with predictions from various Monte Carlo event generators.
Published: 2020

20. Search for light long-lived neutral particles produced in pp collisions at √s=13TeV and decaying into collimated leptons or light hadrons with the ATLAS detector

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adachi, S, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexandre, D, Alexopoulos, T, Alfonsi, A, Alhroob, M, Ali, B, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Estevez, MA, Piqueras, DÁ, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, CF, Anders, JK, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Bella, LA, Arabidze, G, Araque, JP, Ferraz, VA, and Pereira, RA
Subjects: hep-ex, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Quantum Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: Several models of physics beyond the Standard Model predict the existence of dark photons, light neutral particles decaying into collimated leptons or light hadrons. This paper presents a search for long-lived dark photons produced from the decay of a Higgs boson or a heavy scalar boson and decaying into displaced collimated Standard Model fermions. The search uses data corresponding to an integrated luminosity of 36.1 fb- 1 collected in proton–proton collisions at s=13 Te recorded in 2015–2016 with the ATLAS detector at the Large Hadron Collider. The observed number of events is consistent with the expected background, and limits on the production cross section times branching fraction as a function of the proper decay length of the dark photon are reported. A cross section times branching fraction above 4 pb is excluded for a Higgs boson decaying into two dark photons for dark-photon decay lengths between 1.5 mm and 307 mm.
Published: 2020

21. Search for electroweak production of charginos and sleptons decaying into final states with two leptons and missing transverse momentum in √s=13 TeV pp collisions using the ATLAS detector

Author: Aad, G, Abbott, B, Abbott, DC, Abdinov, O, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adachi, S, Adam, L, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexandre, D, Alexopoulos, T, Alfonsi, A, Alhroob, M, Ali, B, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Estevez, MA, Piqueras, DÁ, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, CF, Anders, JK, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Bella, LA, Arabidze, G, Araque, JP, Ferraz, VA, and Pereira, RA
Subjects: hep-ex, Quantum Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: A search for the electroweak production of charginos and sleptons decaying into final states with two electrons or muons is presented. The analysis is based on 139 fb- 1 of proton–proton collisions recorded by the ATLAS detector at the Large Hadron Collider at s=13 TeV. Three R-parity-conserving scenarios where the lightest neutralino is the lightest supersymmetric particle are considered: the production of chargino pairs with decays via either W bosons or sleptons, and the direct production of slepton pairs. The analysis is optimised for the first of these scenarios, but the results are also interpreted in the others. No significant deviations from the Standard Model expectations are observed and limits at 95% confidence level are set on the masses of relevant supersymmetric particles in each of the scenarios. For a massless lightest neutralino, masses up to 420 Ge are excluded for the production of the lightest-chargino pairs assuming W-boson-mediated decays and up to 1 TeV for slepton-mediated decays, whereas for slepton-pair production masses up to 700 Ge are excluded assuming three generations of mass-degenerate sleptons.
Published: 2020

22. Transverse momentum and process dependent azimuthal anisotropies in √sNN=8.16 TeV p+Pb collisions with the ATLAS detector

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adachi, S, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Aliev, M, Alimonti, G, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, F, Alpigiani, C, Alshehri, AA, Estevez, MA, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, CF, Anders, JK, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Bella, LA, Araque, JP, Ferraz, VA, Pereira, RA, Arcangeletti, C, Arce, ATH, and Arduh, FA
Subjects: nucl-ex, hep-ex, Quantum Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: The azimuthal anisotropy of charged particles produced in sNN=8.16 TeV p+Pb collisions is measured with the ATLAS detector at the LHC. The data correspond to an integrated luminosity of 165 nb - 1 that was collected in 2016. Azimuthal anisotropy coefficients, elliptic v2 and triangular v3, extracted using two-particle correlations with a non-flow template fit procedure, are presented as a function of particle transverse momentum (pT) between 0.5 and 50 GeV. The v2 results are also reported as a function of centrality in three different particle pT intervals. The results are reported from minimum-bias events and jet-triggered events, where two jet pT thresholds are used. The anisotropies for particles with pT less than about 2 GeV are consistent with hydrodynamic flow expectations, while the significant non-zero anisotropies for pT in the range 9–50 GeV are not explained within current theoretical frameworks. In the pT range 2–9 GeV, the anisotropies are larger in minimum-bias than in jet-triggered events. Possible origins of these effects, such as the changing admixture of particles from hard scattering and the underlying event, are discussed.
Published: 2020

23. Measurement of long-range two-particle azimuthal correlations in Z-boson tagged pp collisions at √s=8 and 13 TeV

Author: Aaboud, M, Aad, G, Abbott, B, Abbott, DC, Abdinov, O, Abeloos, B, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Adachi, S, Adam, L, Adam Bourdarios, C, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Alberghi, GL, Albert, J, Alconada Verzini, MJ, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexandre, D, Alexopoulos, T, Alhroob, M, Ali, B, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Alstaty, MI, Alvarez Gonzalez, B, Álvarez Piqueras, D, Alviggi, MG, Amaral Coutinho, Y, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Amor Dos Santos, SP, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, CF, Anders, JK, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angelozzi, I, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Aperio Bella, L, Arabidze, G, Araque, JP, Araujo Ferraz, V, Araujo Pereira, R, Arce, ATH, Arduh, FA, Arguin, JF, Argyropoulos, S, and Arling, JH
Subjects: nucl-ex, hep-ex, Nuclear & Particles Physics, Quantum Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: Results are presented from the measurement by ATLAS of long-range (| Δ η| > 2) dihadron angular correlations in s=8 and 13 TeV pp collisions containing a Z boson. The analysis is performed using 19.4 fb - 1 of s=8 TeV data recorded during Run 1 of the LHC and 36.1 fb - 1 of s=13 TeV data recorded during Run 2. Two-particle correlation functions are measured as a function of relative azimuthal angle over the relative pseudorapidity range 2 < | Δ η| < 5 for different intervals of charged-particle multiplicity and transverse momentum. The measurements are corrected for the presence of background charged particles generated by collisions that occur during one passage of two colliding proton bunches in the LHC. Contributions to the two-particle correlation functions from hard processes are removed using a template-fitting procedure. Sinusoidal modulation in the correlation functions is observed and quantified by the second Fourier coefficient of the correlation function, v2 , 2, which in turn is used to obtain the single-particle anisotropy coefficient v2. The v2 values in the Z-tagged events, integrated over 0.5 < pT< 5 GeV, are found to be independent of multiplicity and s, and consistent within uncertainties with previous measurements in inclusive pp collisions. As a function of charged-particle pT, the Z-tagged and inclusive v2 values are consistent within uncertainties for pT< 3 GeV.
Published: 2020

24. Performance of electron and photon triggers in ATLAS during LHC Run 2

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adachi, S, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Aliev, M, Alimonti, G, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Estevez, MA, Piqueras, DÁ, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, CF, Anders, JK, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Bella, LA, Araque, JP, Ferraz, VA, and Pereira, RA
Subjects: hep-ex, Nuclear & Particles Physics, Quantum Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: Electron and photon triggers covering transverse energies from 5 GeV to several TeV are essential for the ATLAS experiment to record signals for a wide variety of physics: from Standard Model processes to searches for new phenomena in both proton–proton and heavy-ion collisions. To cope with a fourfold increase of peak LHC luminosity from 2015 to 2018 (Run 2), to 2.1×1034cm-2s-1, and a similar increase in the number of interactions per beam-crossing to about 60, trigger algorithms and selections were optimised to control the rates while retaining a high efficiency for physics analyses. For proton–proton collisions, the single-electron trigger efficiency relative to a single-electron offline selection is at least 75% for an offline electron of 31 GeV, and rises to 96% at 60 GeV; the trigger efficiency of a 25 GeV leg of the primary diphoton trigger relative to a tight offline photon selection is more than 96% for an offline photon of 30 GeV. For heavy-ion collisions, the primary electron and photon trigger efficiencies relative to the corresponding standard offline selections are at least 84% and 95%, respectively, at 5 GeV above the corresponding trigger threshold.
Published: 2020

25. Measurements of top-quark pair differential and double-differential cross-sections in the ℓ +jets channel with pp collisions at √s=13 TeV using the ATLAS detector

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adachi, S, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexandre, D, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Estevez, MA, Piqueras, DÁ, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, CF, Anders, JK, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Bella, LA, Arabidze, G, Araque, JP, and Ferraz, VA
Subjects: hep-ex, Nuclear & Particles Physics, Quantum Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: Single- and double-differential cross-section measurements are presented for the production of top-quark pairs, in the lepton + jets channel at particle and parton level. Two topologies, resolved and boosted, are considered and the results are presented as a function of several kinematic variables characterising the top and tt¯ system and jet multiplicities. The study was performed using data from pp collisions at centre-of-mass energy of 13 TeV collected in 2015 and 2016 by the ATLAS detector at the CERN Large Hadron Collider (LHC), corresponding to an integrated luminosity of 36fb-1. Due to the large tt¯ cross-section at the LHC, such measurements allow a detailed study of the properties of top-quark production and decay, enabling precision tests of several Monte Carlo generators and fixed-order Standard Model predictions. Overall, there is good agreement between the theoretical predictions and the data.
Published: 2019

26. Measurement of flow harmonics correlations with mean transverse momentum in lead–lead and proton–lead collisions at √sNN=5.02TeV with the ATLAS detector

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adachi, S, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexandre, D, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Estevez, MA, Piqueras, DÁ, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, CF, Anders, JK, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Bella, LA, Arabidze, G, Araque, JP, and Ferraz, VA
Subjects: nucl-ex, hep-ex, Quantum Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: To assess the properties of the quark–gluon plasma formed in ultrarelativistic ion collisions, the ATLAS experiment at the LHC measures a correlation between the mean transverse momentum and the flow harmonics. The analysis uses data samples of lead–lead and proton–lead collisions obtained at the centre-of-mass energy per nucleon pair of 5.02 TeV, corresponding to total integrated luminosities of 22μb-1 and 28nb-1, respectively. The measurement is performed using a modified Pearson correlation coefficient with the charged-particle tracks on an event-by-event basis. The modified Pearson correlation coefficients for the 2nd-, 3rd-, and 4th-order flow harmonics are measured in the lead–lead collisions as a function of event centrality quantified as the number of charged particles or the number of nucleons participating in the collision. The measurements are performed for several intervals of the charged-particle transverse momentum. The correlation coefficients for all studied harmonics exhibit a strong centrality evolution, which only weakly depends on the charged-particle momentum range. In the proton–lead collisions, the modified Pearson correlation coefficient measured for the 2nd-order flow harmonics shows only weak centrality dependence. The lead-lead data is qualitatively described by the predictions based on the hydrodynamical model.
Published: 2019

27. Measurement of KS0 and Λ production in tt¯ dileptonic events in pp collisions at √s= 7 TeV with the ATLAS detector

Author: Aad, G, Abbott, B, Abbott, DC, Abdinov, O, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adachi, S, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexandre, D, Alexopoulos, T, Alfonsi, A, Alhroob, M, Ali, B, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Estevez, MA, Piqueras, DÁ, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, CF, Anders, JK, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Bella, LA, Arabidze, G, Araque, JP, and Ferraz, VA
Subjects: hep-ex, Nuclear & Particles Physics, Quantum Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: Measurements of KS0 and Λ production in tt¯ final states have been performed. They are based on a data sample with integrated luminosity of 4.6 fb - 1 from proton–proton collisions at a centre-of-mass energy of 7 TeV, collected in 2011 with the ATLAS detector at the Large Hadron Collider. Neutral strange particles are separated into three classes, depending on whether they are contained in a jet, with or without a b-tag, or not associated with a selected jet. The aim is to look for differences in their main kinematic distributions. A comparison of data with several Monte Carlo simulations using different hadronisation and fragmentation schemes, colour reconnection models and different tunes for the underlying event has been made. The production of neutral strange particles in tt¯ dileptonic events is found to be well described by current Monte Carlo models for KS0 and Λ production within jets, but not for those produced outside jets.
Published: 2019

28. Measurement of W± boson production in Pb+Pb collisions at √sNN=5.02Te with the ATLAS detector

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adachi, S, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexandre, D, Alexopoulos, T, Alfonsi, A, Alhroob, M, Ali, B, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Estevez, MA, Piqueras, DÁ, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, CF, Anders, JK, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Bella, LA, Arabidze, G, Araque, JP, Ferraz, VA, and Pereira, RA
Subjects: nucl-ex, hep-ex, Nuclear & Particles Physics, Quantum Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: A measurement of W± boson production in Pb+Pb collisions at sNN=5.02Te is reported using data recorded by the ATLAS experiment at the LHC in 2015, corresponding to a total integrated luminosity of 0.49nb-1. The W± bosons are reconstructed in the electron or muon leptonic decay channels. Production yields of leptonically decaying W± bosons, normalised by the total number of minimum-bias events and the nuclear thickness function, are measured within a fiducial region defined by the detector acceptance and the main kinematic requirements. These normalised yields are measured separately for W+ and W- bosons, and are presented as a function of the absolute value of pseudorapidity of the charged lepton and of the collision centrality. The lepton charge asymmetry is also measured as a function of the absolute value of lepton pseudorapidity. In addition, nuclear modification factors are calculated using the W± boson production cross-sections measured in pp collisions. The results are compared with predictions based on next-to-leading-order calculations with CT14 parton distribution functions as well as with predictions obtained with the EPPS16 and nCTEQ15 nuclear parton distribution functions. No dependence of normalised production yields on centrality and a good agreement with predictions are observed for mid-central and central collisions. For peripheral collisions, the data agree with predictions within 1.7 (0.9) standard deviations for W- (W+) bosons.
Published: 2019

29. ATLAS b-jet identification performance and efficiency measurement with tt¯ events in pp collisions at √s=13 TeV

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adachi, S, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexandre, D, Alexopoulos, T, Alfonsi, A, Alhroob, M, Ali, B, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Estevez, MA, Piqueras, DÁ, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, CF, Anders, JK, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Bella, LA, Arabidze, G, Araque, JP, Ferraz, VA, and Pereira, RA
Subjects: hep-ex, Nuclear & Particles Physics, Quantum Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: The algorithms used by the ATLAS Collaboration during Run 2 of the Large Hadron Collider to identify jets containing b-hadrons are presented. The performance of the algorithms is evaluated in the simulation and the efficiency with which these algorithms identify jets containing b-hadrons is measured in collision data. The measurement uses a likelihood-based method in a sample highly enriched in tt¯ events. The topology of the t→ Wb decays is exploited to simultaneously measure both the jet flavour composition of the sample and the efficiency in a transverse momentum range from 20 to 600 GeV. The efficiency measurement is subsequently compared with that predicted by the simulation. The data used in this measurement, corresponding to a total integrated luminosity of 80.5 fb - 1, were collected in proton–proton collisions during the years 2015–2017 at a centre-of-mass energy s= 13 TeV. By simultaneously extracting both the efficiency and jet flavour composition, this measurement significantly improves the precision compared to previous results, with uncertainties ranging from 1 to 8% depending on the jet transverse momentum.
Published: 2019

30. Measurement of W± -boson and Z-boson production cross-sections in pp collisions at √s=2.76 TeV with the ATLAS detector

Author: Aad, G, Abbott, B, Abbott, DC, Abdinov, O, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adachi, S, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexandre, D, Alexopoulos, T, Alfonsi, A, Alhroob, M, Ali, B, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Estevez, MA, Piqueras, DÁ, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, CF, Anders, JK, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Bella, LA, Arabidze, G, Araque, JP, and Ferraz, VA
Subjects: hep-ex, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Quantum Physics
Abstract: The production cross-sections for W± and Z bosons are measured using ATLAS data corresponding to an integrated luminosity of 4.0 pb- 1 collected at a centre-of-mass energy s=2.76 TeV. The decay channels W→ ℓν and Z→ ℓℓ are used, where ℓ can be an electron or a muon. The cross-sections are presented for a fiducial region defined by the detector acceptance and are also extrapolated to the full phase space for the total inclusive production cross-section. The combined (average) total inclusive cross-sections for the electron and muon channels are: σW+→ℓνtot=2312±26(stat.)±27(syst.)±72(lumi.)±30(extr.)pb,σW-→ℓνtot=1399±21(stat.)±17(syst.)±43(lumi.)±21(extr.)pb,σZ→ℓℓtot=323.4±9.8(stat.)±5.0(syst.)±10.0(lumi.)±5.5(extr.)pb.Measured ratios and asymmetries constructed using these cross-sections are also presented. These observables benefit from full or partial cancellation of many systematic uncertainties that are correlated between the different measurements.
Published: 2019

31. Identification of boosted Higgs bosons decaying into b-quark pairs with the ATLAS detector at 13 TeV

Author: Aad, G, Abbott, B, Abbott, DC, Abdinov, O, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adachi, S, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexandre, D, Alexopoulos, T, Alfonsi, A, Alhroob, M, Ali, B, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Estevez, MA, Piqueras, DÁ, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, CF, Anders, JK, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Bella, LA, Arabidze, G, Araque, JP, and Ferraz, VA
Subjects: hep-ex, Quantum Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: This paper describes a study of techniques for identifying Higgs bosons at high transverse momenta decaying into bottom-quark pairs, H→ bb¯ , for proton–proton collision data collected by the ATLAS detector at the Large Hadron Collider at a centre-of-mass energy s=13 TeV. These decays are reconstructed from calorimeter jets found with the anti-ktR= 1.0 jet algorithm. To tag Higgs bosons, a combination of requirements is used: b-tagging of R= 0.2 track-jets matched to the large-R calorimeter jet, and requirements on the jet mass and other jet substructure variables. The Higgs boson tagging efficiency and corresponding multijet and hadronic top-quark background rejections are evaluated using Monte Carlo simulation. Several benchmark tagging selections are defined for different signal efficiency targets. The modelling of the relevant input distributions used to tag Higgs bosons is studied in 36 fb- 1 of data collected in 2015 and 2016 using g→ bb¯ and Z(→ bb¯) γ event selections in data. Both processes are found to be well modelled within the statistical and systematic uncertainties.
Published: 2019

32. Measurement of fiducial and differential W+W- production cross-sections at √s=13 TeV with the ATLAS detector

Author: Aaboud, M, Aad, G, Abbott, B, Abbott, DC, Abdinov, O, Abud, AA, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adachi, S, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Ai, X, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexandre, D, Alexopoulos, T, Alfonsi, A, Alhroob, M, Ali, B, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Alstaty, MI, Estevez, MA, Gonzalez, BA, Piqueras, DÁ, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, CF, Anders, JK, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angelozzi, I, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Bella, LA, and Arabidze, G
Subjects: hep-ex, Nuclear & Particles Physics, Quantum Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: A measurement of fiducial and differential cross-sections for W+W- production in proton–proton collisions at s=13 TeV with the ATLAS experiment at the Large Hadron Collider using data corresponding to an integrated luminosity of 36.1 fb - 1 is presented. Events with one electron and one muon are selected, corresponding to the decay of the diboson system as WW→ e±νμ∓ν. To suppress top-quark background, events containing jets with a transverse momentum exceeding 35 GeV are not included in the measurement phase space. The fiducial cross-section, six differential distributions and the cross-section as a function of the jet-veto transverse momentum threshold are measured and compared with several theoretical predictions. Constraints on anomalous electroweak gauge boson self-interactions are also presented in the framework of a dimension-six effective field theory.
Published: 2019

33. Resolution of the ATLAS muon spectrometer monitored drift tubes in LHC Run 2

Author: Aad, G, Abbott, B, Abbott, DC, Abdinov, O, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, Abouzeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adachi, S, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Al Khoury, K, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexandre, D, Alexopoulos, T, Alfonsi, A, Alhroob, M, Ali, B, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Estevez, MA, Piqueras, DÁ, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Dos Santos, SPA, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, CF, Anders, JK, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Bella, LA, Arabidze, G, Araque, JP, and Ferraz, VA
Subjects: Gaseous detectors, Muon spectrometers, Particle tracking detectors, Wire chambers, hep-ex, Nuclear & Particles Physics, Other Physical Sciences, Physical Sciences, Engineering
Abstract: The momentum measurement capability of the ATLAS muon spectrometer relies fundamentally on the intrinsic single-hit spatial resolution of the monitored drift tube precision tracking chambers. Optimal resolution is achieved with a dedicated calibration program that addresses the specific operating conditions of the 354 000 high-pressure drift tubes in the spectrometer. The calibrations consist of a set of timing offsets and drift time to drift distance transfer relations, and result in chamber resolution functions. This paper describes novel algorithms to obtain precision calibrations from data collected by ATLAS in LHC Run 2 and from a gas monitoring chamber, deployed in a dedicated gas facility. The algorithm output consists of a pair of correction constants per chamber which are applied to baseline calibrations, and determined to be valid for the entire ATLAS Run 2. The final single-hit spatial resolution, averaged over 1172 monitored drift tube chambers, is 81.7 ± 2.2 μm.
Published: 2019

34. Measurement of the cross-section and charge asymmetry of W bosons produced in proton–proton collisions at √s=8TeV with the ATLAS detector

Author: Aad, G, Abbott, B, Abbott, DC, Abdinov, O, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adachi, S, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Ai, X, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexandre, D, Alexopoulos, T, Alfonsi, A, Alhroob, M, Ali, B, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Estevez, MA, Gonzalez, BA, Piqueras, DÁ, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, CF, Anders, JK, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Bella, LA, Arabidze, G, Araque, JP, and Ferraz, VA
Subjects: hep-ex, Nuclear & Particles Physics, Quantum Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: This paper presents measurements of the W+→ μ+ν and W-→ μ-ν cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton–proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2fb-1. The precision of the cross-section measurements varies between 0.8 and 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.
Published: 2019

35. Search for excited electrons singly produced in proton–proton collisions at √s=13Te with the ATLAS experiment at the LHC

Author: Aaboud, M, Aad, G, Abbott, B, Abbott, DC, Abdinov, O, Abeloos, B, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Adachi, S, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexandre, D, Alexopoulos, T, Alhroob, M, Ali, B, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Alstaty, MI, Gonzalez, BA, Piqueras, DÁ, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, CF, Anders, JK, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angelozzi, I, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Bella, LA, Arabidze, G, Araque, JP, Ferraz, VA, Pereira, RA, Arce, ATH, Arduh, FA, Arguin, JF, Argyropoulos, S, and Arling, JH
Subjects: hep-ex, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Quantum Physics
Abstract: A search for excited electrons produced in pp collisions at s = 13 Te via a contact interaction qq¯ → ee∗ is presented. The search uses 36.1 fb- 1 of data collected in 2015 and 2016 by the ATLAS experiment at the Large Hadron Collider. Decays of the excited electron into an electron and a pair of quarks (eqq¯) are targeted in final states with two electrons and two hadronic jets, and decays via a gauge interaction into a neutrino and a W boson (νW) are probed in final states with an electron, missing transverse momentum, and a large-radius jet consistent with a hadronically decaying W boson. No significant excess is observed over the expected backgrounds. Upper limits are calculated for the pp→ ee∗→ eeqq¯ and pp→ ee∗→ eνW production cross sections as a function of the excited electron mass me∗ at 95% confidence level. The limits are translated into lower bounds on the compositeness scale parameter Λ of the model as a function of me∗. For me∗
Published: 2019

36. Measurement of distributions sensitive to the underlying event in inclusive Z boson production in pp collisions at √s = 13 TeV with the ATLAS detector

Author: Aad, G, Abbott, B, Abbott, DC, Abdinov, O, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adachi, S, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexandre, D, Alexopoulos, T, Alfonsi, A, Alhroob, M, Ali, B, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Estevez, MA, Piqueras, DÁ, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, CF, Anders, JK, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Bella, LA, Arabidze, G, Araque, JP, and Ferraz, VA
Subjects: hep-ex, Quantum Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: This paper presents measurements of charged-particle distributions sensitive to the properties of the underlying event in events containing a Z boson decaying into a muon pair. The data were obtained using the ATLAS detector at the LHC in proton–proton collisions at a centre-of-mass energy of 13 Te with an integrated luminosity of 3.2fb-1. Distributions of the charged-particle multiplicity and of the charged-particle transverse momentum are measured in regions of the azimuth defined relative to the Z boson direction. The measured distributions are compared with the predictions of various Monte Carlo generators which implement different underyling event models. The Monte Carlo model predictions qualitatively describe the data well, but with some significant discrepancies.
Published: 2019

37. Electron reconstruction and identification in the ATLAS experiment using the 2015 and 2016 LHC proton–proton collision data at √s=13 TeV

Author: Aaboud, M, Aad, G, Abbott, B, Abbott, DC, Abdinov, O, Abeloos, B, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Adachi, S, Adam, L, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adye, T, Affolder, AA, Afik, Y, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Alberghi, GL, Albert, J, Albicocco, P, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexandre, D, Alexopoulos, T, Alhroob, M, Ali, B, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Alstaty, MI, Gonzalez, BA, Piqueras, DÁ, Alviggi, MG, Amadio, BT, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Ancu, LS, Andari, N, Andeen, T, Anders, CF, Anders, JK, Anderson, KJ, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angelozzi, I, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Bella, LA, Arabidze, G, Araque, JP, Ferraz, VA, Pereira, RA, Arce, ATH, Ardell, RE, and Arduh, FA
Subjects: physics.ins-det, hep-ex, Quantum Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: Algorithms used for the reconstruction and identification of electrons in the central region of the ATLAS detector at the Large Hadron Collider (LHC) are presented in this paper; these algorithms are used in ATLAS physics analyses that involve electrons in the final state and which are based on the 2015 and 2016 proton–proton collision data produced by the LHC at s = 13 TeV. The performance of the electron reconstruction, identification, isolation, and charge identification algorithms is evaluated in data and in simulated samples using electrons from Z→ ee and J/ ψ→ ee decays. Typical examples of combinations of electron reconstruction, identification, and isolation operating points used in ATLAS physics analyses are shown.
Published: 2019

38. Search for long-lived neutral particles in pp collisions at √s=13TeV that decay into displaced hadronic jets in the ATLAS calorimeter

Author: Aaboud, M, Aad, G, Abbott, B, Abbott, DC, Abdinov, O, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Adachi, S, Adam, L, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexandre, D, Alexopoulos, T, Alhroob, M, Ali, B, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Alstaty, MI, Estevez, MA, Gonzalez, BA, Piqueras, DÁ, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Andari, N, Andeen, T, Anders, CF, Anders, JK, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angelozzi, I, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Bella, LA, Arabidze, G, Araque, JP, Ferraz, VA, Pereira, RA, Arce, ATH, Arduh, FA, and Arguin, JF
Subjects: hep-ex, Nuclear & Particles Physics, Quantum Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: This paper describes a search for pairs of neutral, long-lived particles decaying in the ATLAS calorimeter. Long-lived particles occur in many extensions to the Standard Model and may elude searches for new promptly decaying particles. The analysis considers neutral, long-lived scalars with masses between 5 and 400 GeV, produced from decays of heavy bosons with masses between 125 and 1000 GeV, where the long-lived scalars decay into Standard Model fermions. The analysis uses either 10.8fb-1 or 33.0fb-1 of data (depending on the trigger) recorded in 2016 at the LHC with the ATLAS detector in proton–proton collisions at a centre-of-mass energy of 13 TeV. No significant excess is observed, and limits are reported on the production cross section times branching ratio as a function of the proper decay length of the long-lived particles.
Published: 2019

39. Measurements of inclusive and differential fiducial cross-sections of tt¯ γ production in leptonic final states at √s=13TeV in ATLAS

Author: Aaboud, M, Aad, G, Abbott, B, Abbott, DC, Abdinov, O, Abeloos, B, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Adachi, S, Adam, L, Adamczyk, L, Adamek, L, Adelman, J, Adersberger, M, Adiguzel, A, Adye, T, Affolder, AA, Afik, Y, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Alberghi, GL, Albert, J, Albicocco, P, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexandre, D, Alexopoulos, T, Alhroob, M, Ali, B, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Alstaty, MI, Gonzalez, BA, Piqueras, DÁ, Alviggi, MG, Amadio, BT, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Dos Santos, SPA, Amoroso, S, Amrouche, CS, An, F, Anastopoulos, C, Ancu, LS, Andari, N, Andeen, T, Anders, CF, Anders, JK, Anderson, KJ, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angelozzi, I, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Bella, LA, Arabidze, G, Araque, JP, Ferraz, VA, Pereira, RA, Arce, ATH, Ardell, RE, and Arduh, FA
Subjects: hep-ex, Nuclear & Particles Physics, Quantum Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: Inclusive and differential cross-sections for the production of a top-quark pair in association with a photon are measured with proton-proton collision data corresponding to an integrated luminosity of 36.1 fb-1, collected by the ATLAS detector at the LHC in 2015 and 2016 at a centre-of-mass energy of 13 TeV. The measurements are performed in single-lepton and dilepton final states in a fiducial volume. Events with exactly one photon, one or two leptons, a channel-dependent minimum number of jets, and at least one b-jet are selected. Neural network algorithms are used to separate the signal from the backgrounds. The fiducial cross-sections are measured to be 521±9(stat.)±41(sys.)fb and 69±3(stat.)±4(sys.)fb for the single-lepton and dilepton channels, respectively. The differential cross-sections are measured as a function of photon transverse momentum, photon absolute pseudorapidity, and angular distance between the photon and its closest lepton in both channels, as well as azimuthal opening angle and absolute pseudorapidity difference between the two leptons in the dilepton channel. All measurements are in agreement with the theoretical predictions.
Published: 2019

40. Performance of top-quark and W -boson tagging with ATLAS in Run 2 of the LHC

Author: Aaboud, M, Aad, G, Abbott, B, Abdinov, O, Abeloos, B, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Adachi, S, Adam, L, Adamczyk, L, Adelman, J, Adersberger, M, Adiguzel, A, Adye, T, Affolder, AA, Afik, Y, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Alberghi, GL, Albert, J, Albicocco, P, Alconada Verzini, MJ, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alhroob, M, Ali, B, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Alstaty, MI, Alvarez Gonzalez, B, Álvarez Piqueras, D, Alviggi, MG, Amadio, BT, Amaral Coutinho, Y, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Amor Dos Santos, SP, Amoroso, S, Amrouche, CS, Anastopoulos, C, Ancu, LS, Andari, N, Andeen, T, Anders, CF, Anders, JK, Anderson, KJ, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angelozzi, I, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Aperio Bella, L, Arabidze, G, Araque, JP, Araujo Ferraz, V, Araujo Pereira, R, Arce, ATH, Ardell, RE, Arduh, FA, Arguin, JF, Argyropoulos, S, Armbruster, AJ, and Armitage, LJ
Subjects: hep-ex, Quantum Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Nuclear & Particles Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: The performance of identification algorithms (“taggers”) for hadronically decaying top quarks and W bosons in pp collisions at s = 13 TeV recorded by the ATLAS experiment at the Large Hadron Collider is presented. A set of techniques based on jet shape observables are studied to determine a set of optimal cut-based taggers for use in physics analyses. The studies are extended to assess the utility of combinations of substructure observables as a multivariate tagger using boosted decision trees or deep neural networks in comparison with taggers based on two-variable combinations. In addition, for highly boosted top-quark tagging, a deep neural network based on jet constituent inputs as well as a re-optimisation of the shower deconstruction technique is presented. The performance of these taggers is studied in data collected during 2015 and 2016 corresponding to 36.1 fb - 1 for the tt¯ and γ+ jet and 36.7 fb - 1 for the dijet event topologies.
Published: 2019

41. Measurement of the photon identification efficiencies with the ATLAS detector using LHC Run 2 data collected in 2015 and 2016

Author: Aaboud, M, Aad, G, Abbott, B, Abdinov, O, Abeloos, B, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Adachi, S, Adam, L, Adamczyk, L, Adelman, J, Adersberger, M, Adiguzel, A, Adye, T, Affolder, AA, Afik, Y, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Alberghi, GL, Albert, J, Albicocco, P, Alconada Verzini, MJ, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alhroob, M, Ali, B, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Alstaty, MI, Alvarez Gonzalez, B, Álvarez Piqueras, D, Alviggi, MG, Amadio, BT, Amaral Coutinho, Y, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Amor Dos Santos, SP, Amoroso, S, Amrouche, CS, Anastopoulos, C, Ancu, LS, Andari, N, Andeen, T, Anders, CF, Anders, JK, Anderson, KJ, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angelozzi, I, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Aperio Bella, L, Arabidze, G, Araque, JP, Araujo Ferraz, V, Araujo Pereira, R, Arce, ATH, Ardell, RE, Arduh, FA, Arguin, JF, Argyropoulos, S, Armbruster, AJ, and Armitage, LJ
Subjects: hep-ex, Nuclear & Particles Physics, Quantum Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: The efficiency of the photon identification criteria in the ATLAS detector is measured using 36.1fb1 to 36.7fb1 of pp collision data at s=13 TeV collected in 2015 and 2016. The efficiencies are measured separately for converted and unconverted isolated photons, in four different pseudorapidity regions, for transverse momenta between 10 GeV and 1.5 TeV. The results from the combination of three data-driven techniques are compared with the predictions from simulation after correcting the variables describing the shape of electromagnetic showers in simulation for the average differences observed relative to data. Data-to-simulation efficiency ratios are determined to account for the small residual efficiency differences. These factors are measured with uncertainties between 0.5% and 5% depending on the photon transverse momentum and pseudorapidity. The impact of the isolation criteria on the photon identification efficiency, and that of additional soft pp interactions, are also discussed. The probability of reconstructing an electron as a photon candidate is measured in data, and compared with the predictions from simulation. The efficiency of the reconstruction of photon conversions is measured using a sample of photon candidates from Z→ μμγ events, exploiting the properties of the ratio of the energies deposited in the first and second longitudinal layers of the ATLAS electromagnetic calorimeter.
Published: 2019

42. Search for supersymmetry in events with large missing transverse momentum, jets, and at least one tau lepton in 7 TeV proton-proton collision data with the ATLAS detector

Author: Aad, G, Abajyan, T, Abbott, B, Abdallah, J, Khalek, SA, Abdelalim, AA, Abdinov, O, Aben, R, Abi, B, Abolins, M, Zeid, OSA, Abramowicz, H, Abreu, H, Acharya, BS, Adamczyk, L, Adams, DL, Addy, TN, Adelman, J, Adomeit, S, Adragna, P, Adye, T, Aefsky, S, Saavedra, JAA, Agustoni, M, Aharrouche, M, Ahlen, SP, Ahles, F, Ahmad, A, Ahsan, M, Aielli, G, Akdogan, T, Åkesson, TPA, Akimoto, G, Akimov, AV, Alam, MS, Alam, MA, Albert, J, Albrand, S, Aleksa, M, Aleksandrov, IN, Alessandria, F, Alexa, C, Alexander, G, Alexandre, G, Alexopoulos, T, Alhroob, M, Aliev, M, Alimonti, G, Alison, J, Allbrooke, BMM, Allport, PP, Spiers, SEA, Almond, J, Aloisio, A, Alon, R, Alonso, A, Alonso, F, Altheimer, A, Gonzalez, BA, Alviggi, MG, Amako, K, Amelung, C, Ammosov, VV, Dos Santos, SPA, Amorim, A, Amram, N, Anastopoulos, C, Ancu, LS, Andari, N, Andeen, T, Anders, CF, Anders, G, Anderson, KJ, Andreazza, A, Andrei, V, Andrieux, ML, Anduaga, XS, Angelidakis, S, Anger, P, Angerami, A, Anghinolfi, F, Anisenkov, A, Anjos, N, Annovi, A, Antonaki, A, Antonelli, M, Antonov, A, Antos, J, Anulli, F, Aoki, M, Aoun, S, Bella, LA, Apolle, R, Arabidze, G, Aracena, I, Arai, Y, Arce, ATH, Arfaoui, S, Arguin, JF, and Arik, E
Subjects: hep-ex, Nuclear & Particles Physics, Quantum Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Atomic, Molecular, Nuclear, Particle and Plasma Physics
Abstract: A search for supersymmetry (SUSY) in events with large missing transverse momentum, jets, and at least one hadronically decaying τ lepton, with zero or one additional light lepton (e/μ), has been performed using 4.7 fb−1of proton-proton collision data at √s = 7 TeV recorded with the ATLAS detector at the Large Hadron Collider. No excess above the Standard Model background expectation is observed and a 95 % confidence level visible cross-section upper limit for new phenomena is set. In the framework of gauge-mediated SUSY-breaking models, lower limits on the mass scale Λ are set at 54 TeV in the regions where the τ1is the next-to-lightest SUSY particle (tanβ > 20). These limits provide the most stringent tests to date of GMSB models in a large part of the parameter space considered.
Published: 2012

43. Observation of electroweak production of two jets in association with an isolated photon and missing transverse momentum, and search for a Higgs boson decaying into invisible particles at 13 TeV with the ATLAS detector

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, Aboulhorma, A, Abramowicz, H, Abreu, H, Abulaiti, Y, Hoffman, ACA, Acharya, BS, Achkar, B, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Addepalli, SV, Adelman, J, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Agarwala, J, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmad, A, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Aizenberg, I, Akatsuka, S, Akbiyik, M, Åkesson, TPA, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Albicocco, P, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Ali, S, Aliev, M, Alimonti, G, Allaire, C, Allbrooke, BMM, Allport, PP, Aloisio, A, Alonso, F, Alpigiani, C, Camelia, EA, Estevez, MA, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, Anastopoulos, C, Andari, N, Andeen, T, Anders, JK, Andrean, SY, Andreazza, A, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Aparo, MA, Bella, LA, Aranzabal, N, Ferraz, VA, Arcangeletti, C, Arce, ATH, Arena, E, Aad, G [0000-0002-6665-4934], Abbott, B [0000-0002-5888-2734], Abbott, DC [0000-0002-7248-3203], Abud, AA [0000-0002-2788-3822], Abeling, K [0000-0002-1002-1652], Abhayasinghe, DK [0000-0002-2987-4006], Abidi, SH [0000-0002-8496-9294], Aboulhorma, A [0000-0002-9987-2292], Abramowicz, H [0000-0001-5329-6640], Abreu, H [0000-0002-1599-2896], Abulaiti, Y [0000-0003-0403-3697], Hoffman, ACA [0000-0003-0762-7204], Acharya, BS [0000-0002-8588-9157], Achkar, B [0000-0002-0288-2567], Adam, L [0000-0001-6005-2812], Bourdarios, CA [0000-0002-2634-4958], Adamczyk, L [0000-0002-5859-2075], Adamek, L [0000-0003-1562-3502], Addepalli, SV [0000-0002-2919-6663], Adelman, J [0000-0002-1041-3496], Adiguzel, A [0000-0001-6644-0517], Adorni, S [0000-0003-3620-1149], Adye, T [0000-0003-0627-5059], Affolder, AA [0000-0002-9058-7217], Afik, Y [0000-0001-8102-356X], Agapopoulou, C [0000-0002-2368-0147], Agaras, MN [0000-0002-4355-5589], Agarwala, J [0000-0002-4754-7455], Aggarwal, A [0000-0002-1922-2039], Agheorghiesei, C [0000-0003-3695-1847], Aguilar-Saavedra, JA [0000-0002-5475-8920], Ahmad, A [0000-0001-8638-0582], Ahmadov, F [0000-0003-3644-540X], Ahmed, WS [0000-0003-0128-3279], Ai, X [0000-0003-3856-2415], Aielli, G [0000-0002-0573-8114], Aizenberg, I [0000-0003-2150-1624], Akatsuka, S [0000-0002-1681-6405], Akbiyik, M [0000-0002-7342-3130], Åkesson, TPA [0000-0003-4141-5408], Akimov, AV [0000-0002-2846-2958], Khoury, KA [0000-0002-0547-8199], Alberghi, GL [0000-0003-2388-987X], Albert, J [0000-0003-0253-2505], Albicocco, P [0000-0001-6430-1038], Verzini, MJA [0000-0003-2212-7830], Alderweireldt, S [0000-0002-8224-7036], Aleksa, M [0000-0002-1936-9217], Aleksandrov, IN [0000-0001-7381-6762], Alexa, C [0000-0003-0922-7669], Alexopoulos, T [0000-0002-8977-279X], Alfonsi, A [0000-0001-7406-4531], Alfonsi, F [0000-0002-0966-0211], Alhroob, M [0000-0001-7569-7111], Ali, B [0000-0001-8653-5556], Ali, S [0000-0001-5216-3133], Aliev, M [0000-0002-9012-3746], Alimonti, G [0000-0002-7128-9046], Allaire, C [0000-0003-4745-538X], Allbrooke, BMM [0000-0002-5738-2471], Allport, PP [0000-0001-7303-2570], Aloisio, A [0000-0002-3883-6693], Alonso, F [0000-0001-9431-8156], Alpigiani, C [0000-0002-7641-5814], Estevez, MA [0000-0002-8181-6532], Alviggi, MG [0000-0003-0026-982X], Coutinho, YA [0000-0002-1798-7230], Ambler, A [0000-0003-2184-3480], Ambroz, L [0000-0002-0987-6637], Amidei, D [0000-0002-6814-0355], Santos, SPAD [0000-0001-7566-6067], Amoroso, S [0000-0001-5450-0447], Anastopoulos, C [0000-0003-1587-5830], Andari, N [0000-0002-4935-4753], Andeen, T [0000-0002-4413-871X], Anders, JK [0000-0002-1846-0262], Andrean, SY [0000-0002-9766-2670], Andreazza, A [0000-0001-5161-5759], Angelidakis, S [0000-0002-8274-6118], Angerami, A [0000-0001-7834-8750], Anisenkov, AV [0000-0002-7201-5936], Annovi, A [0000-0002-4649-4398], Antel, C [0000-0001-9683-0890], Anthony, MT [0000-0002-5270-0143], Antipov, E [0000-0002-6678-7665], Antonelli, M [0000-0002-2293-5726], Antrim, DJA [0000-0001-8084-7786], Anulli, F [0000-0003-2734-130X], Aoki, M [0000-0001-7498-0097], Pozo, JAA [0000-0001-7401-4331], Aparo, MA [0000-0003-4675-7810], Bella, LA [0000-0003-3942-1702], Aranzabal, N [0000-0001-9013-2274], Ferraz, VA [0000-0003-1177-7563], Arcangeletti, C [0000-0001-8648-2896], Arce, ATH [0000-0002-7255-0832], Arena, E [0000-0001-5970-8677], and Apollo - University of Cambridge Repository
Subjects: Quantum Physics, Particle and Plasma Physics, hep-ex, High Energy Physics::Phenomenology, Molecular, Nuclear, High Energy Physics::Experiment, Atomic, Nuclear & Particles Physics
Abstract: This paper presents a measurement of the electroweak production of two jets in association with a $Z\gamma$ pair, with the $Z$ boson decaying into two neutrinos. It also presents a search for invisible or partially invisible decays of a Higgs boson with a mass of 125 GeV produced through vector-boson fusion with a photon in the final state. These results use data from LHC proton-proton collisions at $\sqrt{s}$ = 13 TeV collected with the ATLAS detector and corresponding to an integrated luminosity of 139 fb$^{-1}$. The event signature, shared by all benchmark processes considered for the measurements and searches, is characterized by a significant amount of unbalanced transverse momentum and a photon in the final state, in addition to a pair of forward jets. Electroweak $Z\gamma$ production in association with two jets is observed in this final state with a significance of 5.2 (5.1 expected) standard deviations. The measured fiducial cross-section for this process is 1.31$\pm$0.29 fb. An observed (expected) upper limit of 0.37 ($0.34^{+0.15}_{-0.10}$) at 95% confidence level is set on the branching ratio of a 125 GeV Higgs boson to invisible particles, assuming the Standard Model production cross-section. The signature is also interpreted in the context of decays of a Higgs boson into a photon and a dark photon. An observed (expected) 95% CL upper limit on the branching ratio for this decay is set at 0.018 ($0.017^{+0.007}_{-0.005}$), assuming the Standard Model production cross-section for a 125 GeV Higgs boson.
Published: 2022
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44. Performance of the ATLAS Level-1 topological trigger in Run 2

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Hoffman, ACA, Acharya, BS, Achkar, B, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmad, A, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Akbiyik, M, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Ali, S, Aliev, M, Alimonti, G, Allaire, C, Allbrooke, BMM, Allport, PP, Aloisio, A, Alonso, F, Alpigiani, C, Camelia, EA, Estevez, MA, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, Anastopoulos, C, Andari, N, Andeen, T, Anders, JK, Andrean, SY, Andreazza, A, Andrei, V, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Aparo, MA, Bella, LA, Aranzabal, N, Ferraz, VA, Arcangeletti, C, Arce, ATH, Arguin, JF, Argyropoulos, S, Aad, G [0000-0002-6665-4934], Abbott, B [0000-0002-5888-2734], Abbott, DC [0000-0002-7248-3203], Abud, AA [0000-0002-2788-3822], Abeling, K [0000-0002-1002-1652], Abhayasinghe, DK [0000-0002-2987-4006], Abidi, SH [0000-0002-8496-9294], AbouZeid, OS [0000-0002-8279-9324], Abramowicz, H [0000-0001-5329-6640], Abreu, H [0000-0002-1599-2896], Abulaiti, Y [0000-0003-0403-3697], Hoffman, ACA [0000-0003-0762-7204], Acharya, BS [0000-0002-8588-9157], Achkar, B [0000-0002-0288-2567], Adam, L [0000-0001-6005-2812], Bourdarios, CA [0000-0002-2634-4958], Adamczyk, L [0000-0002-5859-2075], Adamek, L [0000-0003-1562-3502], Adelman, J [0000-0002-1041-3496], Adiguzel, A [0000-0001-6644-0517], Adorni, S [0000-0003-3620-1149], Adye, T [0000-0003-0627-5059], Affolder, AA [0000-0002-9058-7217], Afik, Y [0000-0001-8102-356X], Agapopoulou, C [0000-0002-2368-0147], Agaras, MN [0000-0002-4355-5589], Aggarwal, A [0000-0002-1922-2039], Agheorghiesei, C [0000-0003-3695-1847], Aguilar-Saavedra, JA [0000-0002-5475-8920], Ahmad, A [0000-0001-8638-0582], Ahmadov, F [0000-0003-3644-540X], Ahmed, WS [0000-0003-0128-3279], Ai, X [0000-0003-3856-2415], Aielli, G [0000-0002-0573-8114], Akatsuka, S [0000-0002-1681-6405], Akbiyik, M [0000-0002-7342-3130], Åkesson, TPA [0000-0003-4141-5408], Akilli, E [0000-0003-1309-5937], Akimov, AV [0000-0002-2846-2958], Khoury, KA [0000-0002-0547-8199], Alberghi, GL [0000-0003-2388-987X], Albert, J [0000-0003-0253-2505], Verzini, MJA [0000-0003-2212-7830], Alderweireldt, S [0000-0002-8224-7036], Aleksa, M [0000-0002-1936-9217], Aleksandrov, IN [0000-0001-7381-6762], Alexa, C [0000-0003-0922-7669], Alexopoulos, T [0000-0002-8977-279X], Alfonsi, A [0000-0001-7406-4531], Alfonsi, F [0000-0002-0966-0211], Alhroob, M [0000-0001-7569-7111], Ali, B [0000-0001-8653-5556], Ali, S [0000-0001-5216-3133], Aliev, M [0000-0002-9012-3746], Alimonti, G [0000-0002-7128-9046], Allaire, C [0000-0003-4745-538X], Allbrooke, BMM [0000-0002-5738-2471], Allport, PP [0000-0001-7303-2570], Aloisio, A [0000-0002-3883-6693], Alonso, F [0000-0001-9431-8156], Alpigiani, C [0000-0002-7641-5814], Estevez, MA [0000-0002-8181-6532], Alviggi, MG [0000-0003-0026-982X], Coutinho, YA [0000-0002-1798-7230], Ambler, A [0000-0003-2184-3480], Ambroz, L [0000-0002-0987-6637], Amidei, D [0000-0002-6814-0355], Santos, SPAD [0000-0001-7566-6067], Amoroso, S [0000-0001-5450-0447], Anastopoulos, C [0000-0003-1587-5830], Andari, N [0000-0002-4935-4753], Andeen, T [0000-0002-4413-871X], Anders, JK [0000-0002-1846-0262], Andrean, SY [0000-0002-9766-2670], Andreazza, A [0000-0001-5161-5759], Angelidakis, S [0000-0002-8274-6118], Angerami, A [0000-0001-7834-8750], Anisenkov, AV [0000-0002-7201-5936], Annovi, A [0000-0002-4649-4398], Antel, C [0000-0001-9683-0890], Anthony, MT [0000-0002-5270-0143], Antipov, E [0000-0002-6678-7665], Antonelli, M [0000-0002-2293-5726], Antrim, DJA [0000-0001-8084-7786], Anulli, F [0000-0003-2734-130X], Aoki, M [0000-0001-7498-0097], Pozo, JAA [0000-0001-7401-4331], Aparo, MA [0000-0003-4675-7810], Bella, LA [0000-0003-3942-1702], Aranzabal, N [0000-0001-9013-2274], Ferraz, VA [0000-0003-1177-7563], Arcangeletti, C [0000-0001-8648-2896], Arce, ATH [0000-0002-7255-0832], Arguin, JF [0000-0003-0229-3858], Argyropoulos, S [0000-0001-7748-1429], and Apollo - University of Cambridge Repository
Subjects: hep-ex
Abstract: During LHC Run 2 (2015-2018) the ATLAS Level-1 topological trigger allowed efficient data-taking by the ATLAS experiment at luminosities up to 2.1x10$^{34}$ cm$^{-2}$s$^{-1}$, which exceeds the design value by a factor of two. The system was installed in 2016 and operated in 2017 and 2018. It uses Field Programmable Gate Array processors to select interesting events by placing kinematic and angular requirements on electromagnetic clusters, jets, $\tau$-leptons, muons and the total energy. It significantly improves the background event rejection and signal event acceptance, in particular for Higgs boson and $B$-physics measurements.
Published: 2022

45. Search for long-lived charginos based on a disappearing-track signature using 136 fb - 1 of pp collisions at √s = 13 TeV with the ATLAS detector

Author: Aad, G, Abbott, B, Abbott, DC, Abed Abud, A, Abeling, K, Abhayasinghe, DK, Abidi, SH, Abramowicz, H, Abreu, H, Abulaiti, Y, Abusleme Hoffman, AC, Acharya, BS, Achkar, B, Adam, L, Adam Bourdarios, C, Adamczyk, L, Adamek, L, Adelman, J, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Agarwala, J, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmad, A, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Akbiyik, M, Åkesson, TPA, Akimov, AV, Al Khoury, K, Alberghi, GL, Albert, J, Alconada Verzini, MJ, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Ali, S, Aliev, M, Alimonti, G, Allaire, C, Allbrooke, BMM, Allport, PP, Aloisio, A, Alonso, F, Alpigiani, C, Camelia, EA, Alvarez Estevez, M, Alviggi, MG, Amaral Coutinho, Y, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Amor Dos Santos, SP, Amoroso, S, Amrouche, CS, Anastopoulos, C, Andari, N, Andeen, T, Anders, JK, Andrean, SY, Andreazza, A, Andrei, V, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Aparo, MA, Aperio Bella, L, Aranzabal, N, Araujo Ferraz, V, Arcangeletti, C, Arce, ATH, Arena, E, Arguin, JF, Argyropoulos, S, Arling, JH, Aad, G [0000-0002-6665-4934], Abbott, B [0000-0002-5888-2734], Abbott, DC [0000-0002-7248-3203], Abed Abud, A [0000-0002-2788-3822], Abeling, K [0000-0002-1002-1652], Abhayasinghe, DK [0000-0002-2987-4006], Abidi, SH [0000-0002-8496-9294], Abramowicz, H [0000-0001-5329-6640], Abreu, H [0000-0002-1599-2896], Abulaiti, Y [0000-0003-0403-3697], Abusleme Hoffman, AC [0000-0003-0762-7204], Acharya, BS [0000-0002-8588-9157], Achkar, B [0000-0002-0288-2567], Adam, L [0000-0001-6005-2812], Adam Bourdarios, C [0000-0002-2634-4958], Adamczyk, L [0000-0002-5859-2075], Adamek, L [0000-0003-1562-3502], Adelman, J [0000-0002-1041-3496], Adiguzel, A [0000-0001-6644-0517], Adorni, S [0000-0003-3620-1149], Adye, T [0000-0003-0627-5059], Affolder, AA [0000-0002-9058-7217], Afik, Y [0000-0001-8102-356X], Agapopoulou, C [0000-0002-2368-0147], Agaras, MN [0000-0002-4355-5589], Agarwala, J [0000-0002-4754-7455], Aggarwal, A [0000-0002-1922-2039], Agheorghiesei, C [0000-0003-3695-1847], Aguilar-Saavedra, JA [0000-0002-5475-8920], Ahmad, A [0000-0001-8638-0582], Ahmadov, F [0000-0003-3644-540X], Ahmed, WS [0000-0003-0128-3279], Ai, X [0000-0003-3856-2415], Aielli, G [0000-0002-0573-8114], Akatsuka, S [0000-0002-1681-6405], Akbiyik, M [0000-0002-7342-3130], Åkesson, TPA [0000-0003-4141-5408], Akimov, AV [0000-0002-2846-2958], Al Khoury, K [0000-0002-0547-8199], Alberghi, GL [0000-0003-2388-987X], Albert, J [0000-0003-0253-2505], Alconada Verzini, MJ [0000-0003-2212-7830], Alderweireldt, S [0000-0002-8224-7036], Aleksa, M [0000-0002-1936-9217], Aleksandrov, IN [0000-0001-7381-6762], Alexa, C [0000-0003-0922-7669], Alexopoulos, T [0000-0002-8977-279X], Alfonsi, A [0000-0001-7406-4531], Alfonsi, F [0000-0002-0966-0211], Alhroob, M [0000-0001-7569-7111], Ali, B [0000-0001-8653-5556], Ali, S [0000-0001-5216-3133], Aliev, M [0000-0002-9012-3746], Alimonti, G [0000-0002-7128-9046], Allaire, C [0000-0003-4745-538X], Allbrooke, BMM [0000-0002-5738-2471], Allport, PP [0000-0001-7303-2570], Aloisio, A [0000-0002-3883-6693], Alonso, F [0000-0001-9431-8156], Alpigiani, C [0000-0002-7641-5814], Alvarez Estevez, M [0000-0002-8181-6532], Alviggi, MG [0000-0003-0026-982X], Amaral Coutinho, Y [0000-0002-1798-7230], Ambler, A [0000-0003-2184-3480], Ambroz, L [0000-0002-0987-6637], Amidei, D [0000-0002-6814-0355], Amor Dos Santos, SP [0000-0001-7566-6067], Amoroso, S [0000-0001-5450-0447], Anastopoulos, C [0000-0003-1587-5830], Andari, N [0000-0002-4935-4753], Andeen, T [0000-0002-4413-871X], Anders, JK [0000-0002-1846-0262], Andrean, SY [0000-0002-9766-2670], Andreazza, A [0000-0001-5161-5759], Angelidakis, S [0000-0002-8274-6118], Angerami, A [0000-0001-7834-8750], Anisenkov, AV [0000-0002-7201-5936], Annovi, A [0000-0002-4649-4398], Antel, C [0000-0001-9683-0890], Anthony, MT [0000-0002-5270-0143], Antipov, E [0000-0002-6678-7665], Antonelli, M [0000-0002-2293-5726], Antrim, DJA [0000-0001-8084-7786], Anulli, F [0000-0003-2734-130X], Aoki, M [0000-0001-7498-0097], Pozo, JAA [0000-0001-7401-4331], Aparo, MA [0000-0003-4675-7810], Aperio Bella, L [0000-0003-3942-1702], Aranzabal, N [0000-0001-9013-2274], Araujo Ferraz, V [0000-0003-1177-7563], Arcangeletti, C [0000-0001-8648-2896], Arce, ATH [0000-0002-7255-0832], Arena, E [0000-0001-5970-8677], Arguin, JF [0000-0003-0229-3858], Argyropoulos, S [0000-0001-7748-1429], Arling, JH [0000-0002-1577-5090], and Apollo - University of Cambridge Repository
Subjects: Regular Article - Experimental Physics, hep-ex
Abstract: A search for long-lived charginos produced either directly or in the cascade decay of heavy prompt gluino states is presented. The search is based on proton-proton collision data collected at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV between 2015 and 2018 with the ATLAS detector at the LHC, corresponding to an integrated luminosity of 136 fb$^{-1}$. Long-lived charginos are characterised by a distinct signature of a short and then disappearing track, and are reconstructed using at least four measurements in the ATLAS pixel detector, with no subsequent measurements in the silicon-microstrip tracking volume nor any associated energy deposits in the calorimeter. The final state is complemented by a large missing transverse-momentum requirement for triggering purposes and at least one high-transverse-momentum jet. No excess above the expected backgrounds is observed. Exclusion limits are set at 95% confidence level on the masses of the chargino and gluino for different chargino lifetimes. Chargino masses up to 660 (210) GeV are excluded in scenarios where the chargino is a pure wino (higgsino). For charginos produced during the cascade decay of a heavy gluino, gluinos with masses below 2.1 TeV are excluded for a chargino mass of 300 GeV and a lifetime of 0.2 ns.
Published: 2022

46. Measurement of the energy asymmetry in tt¯ j production at 13 TeV with the ATLAS experiment and interpretation in the SMEFT framework

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, Aboulhorma, A, Abramowicz, H, Abreu, H, Abulaiti, Y, Hoffman, ACA, Acharya, BS, Achkar, B, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Addepalli, SV, Adelman, J, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Agarwala, J, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmad, A, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Aizenberg, I, Akatsuka, S, Akbiyik, M, Åkesson, TPA, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Albicocco, P, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Ali, S, Aliev, M, Alimonti, G, Allaire, C, Allbrooke, BMM, Allport, PP, Aloisio, A, Alonso, F, Alpigiani, C, Camelia, EA, Estevez, MA, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amos, KR, Amrouche, CS, Ananiev, V, Anastopoulos, C, Andari, N, Andeen, T, Anders, JK, Andrean, SY, Andreazza, A, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Aparo, MA, Bella, LA, Aranzabal, N, Ferraz, VA, Arcangeletti, C, Aad, G [0000-0002-6665-4934], Abbott, B [0000-0002-5888-2734], Abbott, DC [0000-0002-7248-3203], Abud, AA [0000-0002-2788-3822], Abeling, K [0000-0002-1002-1652], Abhayasinghe, DK [0000-0002-2987-4006], Abidi, SH [0000-0002-8496-9294], Aboulhorma, A [0000-0002-9987-2292], Abramowicz, H [0000-0001-5329-6640], Abreu, H [0000-0002-1599-2896], Abulaiti, Y [0000-0003-0403-3697], Hoffman, ACA [0000-0003-0762-7204], Acharya, BS [0000-0002-8588-9157], Achkar, B [0000-0002-0288-2567], Adam, L [0000-0001-6005-2812], Bourdarios, CA [0000-0002-2634-4958], Adamczyk, L [0000-0002-5859-2075], Adamek, L [0000-0003-1562-3502], Addepalli, SV [0000-0002-2919-6663], Adelman, J [0000-0002-1041-3496], Adiguzel, A [0000-0001-6644-0517], Adorni, S [0000-0003-3620-1149], Adye, T [0000-0003-0627-5059], Affolder, AA [0000-0002-9058-7217], Afik, Y [0000-0001-8102-356X], Agapopoulou, C [0000-0002-2368-0147], Agaras, MN [0000-0002-4355-5589], Agarwala, J [0000-0002-4754-7455], Aggarwal, A [0000-0002-1922-2039], Agheorghiesei, C [0000-0003-3695-1847], Aguilar-Saavedra, JA [0000-0002-5475-8920], Ahmad, A [0000-0001-8638-0582], Ahmadov, F [0000-0003-3644-540X], Ahmed, WS [0000-0003-0128-3279], Ai, X [0000-0003-3856-2415], Aielli, G [0000-0002-0573-8114], Aizenberg, I [0000-0003-2150-1624], Akatsuka, S [0000-0002-1681-6405], Akbiyik, M [0000-0002-7342-3130], Åkesson, TPA [0000-0003-4141-5408], Akimov, AV [0000-0002-2846-2958], Khoury, KA [0000-0002-0547-8199], Alberghi, GL [0000-0003-2388-987X], Albert, J [0000-0003-0253-2505], Albicocco, P [0000-0001-6430-1038], Verzini, MJA [0000-0003-2212-7830], Alderweireldt, S [0000-0002-8224-7036], Aleksa, M [0000-0002-1936-9217], Aleksandrov, IN [0000-0001-7381-6762], Alexa, C [0000-0003-0922-7669], Alexopoulos, T [0000-0002-8977-279X], Alfonsi, A [0000-0001-7406-4531], Alfonsi, F [0000-0002-0966-0211], Alhroob, M [0000-0001-7569-7111], Ali, B [0000-0001-8653-5556], Ali, S [0000-0001-5216-3133], Aliev, M [0000-0002-9012-3746], Alimonti, G [0000-0002-7128-9046], Allaire, C [0000-0003-4745-538X], Allbrooke, BMM [0000-0002-5738-2471], Allport, PP [0000-0001-7303-2570], Aloisio, A [0000-0002-3883-6693], Alonso, F [0000-0001-9431-8156], Alpigiani, C [0000-0002-7641-5814], Estevez, MA [0000-0002-8181-6532], Alviggi, MG [0000-0003-0026-982X], Coutinho, YA [0000-0002-1798-7230], Ambler, A [0000-0003-2184-3480], Ambroz, L [0000-0002-0987-6637], Amidei, D [0000-0002-6814-0355], Santos, SPAD [0000-0001-7566-6067], Amoroso, S [0000-0001-5450-0447], Amos, KR [0000-0003-1757-5620], Ananiev, V [0000-0003-3649-7621], Anastopoulos, C [0000-0003-1587-5830], Andari, N [0000-0002-4935-4753], Andeen, T [0000-0002-4413-871X], Anders, JK [0000-0002-1846-0262], Andrean, SY [0000-0002-9766-2670], Andreazza, A [0000-0001-5161-5759], Angelidakis, S [0000-0002-8274-6118], Angerami, A [0000-0001-7834-8750], Anisenkov, AV [0000-0002-7201-5936], Annovi, A [0000-0002-4649-4398], Antel, C [0000-0001-9683-0890], Anthony, MT [0000-0002-5270-0143], Antipov, E [0000-0002-6678-7665], Antonelli, M [0000-0002-2293-5726], Antrim, DJA [0000-0001-8084-7786], Anulli, F [0000-0003-2734-130X], Aoki, M [0000-0001-7498-0097], Pozo, JAA [0000-0001-7401-4331], Aparo, MA [0000-0003-4675-7810], Bella, LA [0000-0003-3942-1702], Aranzabal, N [0000-0001-9013-2274], Ferraz, VA [0000-0003-1177-7563], Arcangeletti, C [0000-0001-8648-2896], and Apollo - University of Cambridge Repository
Subjects: hep-ex, High Energy Physics::Phenomenology, High Energy Physics::Experiment
Abstract: A measurement of the energy asymmetry in jet-associated top-quark pair production is presented using 139 $\mathrm{fb}^{-1}$ of data collected by the ATLAS detector at the Large Hadron Collider during $pp$ collisions at $\sqrt{s}=13$ TeV. The observable measures the different probability of top and antitop quarks to have the higher energy as a function of the jet scattering angle with respect to the beam axis. The energy asymmetry is measured in the semileptonic $t\bar{t}$ decay channel, and the hadronically decaying top quark must have transverse momentum above $350$ GeV. The results are corrected for detector effects to particle level in three bins of the scattering angle of the associated jet. The measurement agrees with the SM prediction at next-to-leading-order accuracy in quantum chromodynamics in all three bins. In the bin with the largest expected asymmetry, where the jet is emitted perpendicular to the beam, the energy asymmetry is measured to be $-0.043\pm0.020$, in agreement with the SM prediction of $-0.037\pm0.003$. Interpreting this result in the framework of the Standard Model effective field theory (SMEFT), it is shown that the energy asymmetry is sensitive to the top-quark chirality in four-quark operators and is therefore a valuable new observable in global SMEFT fits.
Published: 2022

47. Constraints on Higgs boson properties using WW∗(→ eνμν) jj production in 36.1fb-1 of √s=13 TeV pp collisions with the ATLAS detector

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmad, A, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Akbiyik, M, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Ali, S, Aliev, M, Alimonti, G, Allaire, C, Allbrooke, BMM, Allport, PP, Aloisio, A, Alonso, F, Alpigiani, C, Camelia, EA, Estevez, MA, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, Anastopoulos, C, Andari, N, Andeen, T, Anders, JK, Andrean, SY, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Aparo, MA, Bella, LA, Aranzabal, N, Ferraz, VA, Pereira, RA, Arcangeletti, C, Arce, ATH, Arguin, JF, Aad, G [0000-0002-6665-4934], Abbott, B [0000-0002-5888-2734], Abbott, DC [0000-0002-7248-3203], Abud, AA [0000-0002-2788-3822], Abeling, K [0000-0002-1002-1652], Abhayasinghe, DK [0000-0002-2987-4006], Abidi, SH [0000-0002-8496-9294], AbouZeid, OS [0000-0002-8279-9324], Abramowicz, H [0000-0001-5329-6640], Abreu, H [0000-0002-1599-2896], Abulaiti, Y [0000-0003-0403-3697], Acharya, BS [0000-0002-8588-9157], Achkar, B [0000-0002-0288-2567], Adam, L [0000-0001-6005-2812], Bourdarios, CA [0000-0002-2634-4958], Adamczyk, L [0000-0002-5859-2075], Adamek, L [0000-0003-1562-3502], Adelman, J [0000-0002-1041-3496], Adiguzel, A [0000-0001-6644-0517], Adorni, S [0000-0003-3620-1149], Adye, T [0000-0003-0627-5059], Affolder, AA [0000-0002-9058-7217], Afik, Y [0000-0001-8102-356X], Agapopoulou, C [0000-0002-2368-0147], Agaras, MN [0000-0002-4355-5589], Aggarwal, A [0000-0002-1922-2039], Agheorghiesei, C [0000-0003-3695-1847], Aguilar-Saavedra, JA [0000-0002-5475-8920], Ahmad, A [0000-0001-8638-0582], Ahmadov, F [0000-0003-3644-540X], Ahmed, WS [0000-0003-0128-3279], Ai, X [0000-0003-3856-2415], Aielli, G [0000-0002-0573-8114], Akatsuka, S [0000-0002-1681-6405], Akbiyik, M [0000-0002-7342-3130], Åkesson, TPA [0000-0003-4141-5408], Akilli, E [0000-0003-1309-5937], Akimov, AV [0000-0002-2846-2958], Khoury, KA [0000-0002-0547-8199], Alberghi, GL [0000-0003-2388-987X], Albert, J [0000-0003-0253-2505], Verzini, MJA [0000-0003-2212-7830], Alderweireldt, S [0000-0002-8224-7036], Aleksa, M [0000-0002-1936-9217], Aleksandrov, IN [0000-0001-7381-6762], Alexa, C [0000-0003-0922-7669], Alexopoulos, T [0000-0002-8977-279X], Alfonsi, A [0000-0001-7406-4531], Alfonsi, F [0000-0002-0966-0211], Alhroob, M [0000-0001-7569-7111], Ali, B [0000-0001-8653-5556], Ali, S [0000-0001-5216-3133], Aliev, M [0000-0002-9012-3746], Alimonti, G [0000-0002-7128-9046], Allaire, C [0000-0003-4745-538X], Allbrooke, BMM [0000-0002-5738-2471], Allport, PP [0000-0001-7303-2570], Aloisio, A [0000-0002-3883-6693], Alonso, F [0000-0001-9431-8156], Alpigiani, C [0000-0002-7641-5814], Estevez, MA [0000-0002-8181-6532], Alviggi, MG [0000-0003-0026-982X], Coutinho, YA [0000-0002-1798-7230], Ambler, A [0000-0003-2184-3480], Ambroz, L [0000-0002-0987-6637], Amidei, D [0000-0002-6814-0355], Santos, SPAD [0000-0001-7566-6067], Amoroso, S [0000-0001-5450-0447], Anastopoulos, C [0000-0003-1587-5830], Andari, N [0000-0002-4935-4753], Andeen, T [0000-0002-4413-871X], Anders, JK [0000-0002-1846-0262], Andrean, SY [0000-0002-9766-2670], Andreazza, A [0000-0001-5161-5759], Angelidakis, S [0000-0002-8274-6118], Angerami, A [0000-0001-7834-8750], Anisenkov, AV [0000-0002-7201-5936], Annovi, A [0000-0002-4649-4398], Antel, C [0000-0001-9683-0890], Anthony, MT [0000-0002-5270-0143], Antipov, E [0000-0002-6678-7665], Antonelli, M [0000-0002-2293-5726], Antrim, DJA [0000-0001-8084-7786], Anulli, F [0000-0003-2734-130X], Aoki, M [0000-0001-7498-0097], Pozo, JAA [0000-0001-7401-4331], Aparo, MA [0000-0003-4675-7810], Bella, LA [0000-0003-3942-1702], Aranzabal, N [0000-0001-9013-2274], Ferraz, VA [0000-0003-1177-7563], Arcangeletti, C [0000-0001-8648-2896], Arce, ATH [0000-0002-7255-0832], Arguin, JF [0000-0003-0229-3858], and Apollo - University of Cambridge Repository
Subjects: Regular Article - Experimental Physics, hep-ex
Abstract: This article presents the results of two studies of Higgs boson properties using the $WW^*(\rightarrow e\nu\mu\nu)jj$ final state, based on a dataset corresponding to 36.1/fb of $\sqrt{s}$=13 TeV proton$-$proton collisions recorded by the ATLAS experiment at the Large Hadron Collider. The first study targets Higgs boson production via gluon$-$gluon fusion and constrains the CP properties of the effective Higgs$-$gluon interaction. Using angular distributions and the overall rate, a value of $\tan(\alpha) = 0.0 \pm 0.4$ stat. $ \pm 0.3$ syst is obtained for the tangent of the mixing angle for CP-even and CP-odd contributions. The second study exploits the vector-boson fusion production mechanism to probe the Higgs boson couplings to longitudinally and transversely polarised $W$ and $Z$ bosons in both the production and the decay of the Higgs boson; these couplings have not been directly constrained previously. The polarisation-dependent coupling-strength scale factors are defined as the ratios of the measured polarisation-dependent coupling strengths to those predicted by the Standard Model, and are determined using rate and kinematic information to be $a_L=0.91^{+0.10}_{-0.18}$(stat.)$^{+0.09}_{-0.17}$(syst.) and $a_{T}=1.2 \pm 0.4 $(stat.)$ ^{+0.2}_{-0.3} $(syst.). These coupling strengths are translated into pseudo-observables, resulting in $\kappa_{VV}= 0.91^{+0.10}_{-0.18}$(stat.)$^{+0.09}_{-0.17}$(syst.) and $\epsilon_{VV} =0.13^{+0.28}_{-0.20}$ (stat.)$^{+0.08}_{-0.10}$(syst.). All results are consistent with the Standard Model predictions.
Published: 2022

48. Determination of the parton distribution functions of the proton using diverse ATLAS data from pp collisions at √s=7 , 8 and 13 TeV

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, Aboulhorma, A, Abramowicz, H, Abreu, H, Abulaiti, Y, Hoffman, ACA, Acharya, BS, Achkar, B, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Addepalli, SV, Adelman, J, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Agarwala, J, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmad, A, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Aizenberg, I, Akbiyik, M, Åkesson, TPA, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Albicocco, P, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Ali, S, Aliev, M, Alimonti, G, Allaire, C, Allbrooke, BMM, Allport, PP, Aloisio, A, Alonso, F, Alpigiani, C, Camelia, EA, Estevez, MA, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amos, KR, Amrouche, CS, Ananiev, V, Anastopoulos, C, Andari, N, Andeen, T, Anders, JK, Andrean, SY, Andreazza, A, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Aparo, MA, Bella, LA, Aranzabal, N, Ferraz, VA, Arcangeletti, C, Arce, ATH, Aad, G [0000-0002-6665-4934], Abbott, B [0000-0002-5888-2734], Abbott, DC [0000-0002-7248-3203], Abud, AA [0000-0002-2788-3822], Abeling, K [0000-0002-1002-1652], Abhayasinghe, DK [0000-0002-2987-4006], Abidi, SH [0000-0002-8496-9294], Aboulhorma, A [0000-0002-9987-2292], Abramowicz, H [0000-0001-5329-6640], Abreu, H [0000-0002-1599-2896], Abulaiti, Y [0000-0003-0403-3697], Hoffman, ACA [0000-0003-0762-7204], Acharya, BS [0000-0002-8588-9157], Achkar, B [0000-0002-0288-2567], Adam, L [0000-0001-6005-2812], Bourdarios, CA [0000-0002-2634-4958], Adamczyk, L [0000-0002-5859-2075], Adamek, L [0000-0003-1562-3502], Addepalli, SV [0000-0002-2919-6663], Adelman, J [0000-0002-1041-3496], Adiguzel, A [0000-0001-6644-0517], Adorni, S [0000-0003-3620-1149], Adye, T [0000-0003-0627-5059], Affolder, AA [0000-0002-9058-7217], Afik, Y [0000-0001-8102-356X], Agapopoulou, C [0000-0002-2368-0147], Agaras, MN [0000-0002-4355-5589], Agarwala, J [0000-0002-4754-7455], Aggarwal, A [0000-0002-1922-2039], Agheorghiesei, C [0000-0003-3695-1847], Aguilar-Saavedra, JA [0000-0002-5475-8920], Ahmad, A [0000-0001-8638-0582], Ahmadov, F [0000-0003-3644-540X], Ahmed, WS [0000-0003-0128-3279], Ai, X [0000-0003-3856-2415], Aielli, G [0000-0002-0573-8114], Aizenberg, I [0000-0003-2150-1624], Akbiyik, M [0000-0002-7342-3130], Åkesson, TPA [0000-0003-4141-5408], Akimov, AV [0000-0002-2846-2958], Khoury, KA [0000-0002-0547-8199], Alberghi, GL [0000-0003-2388-987X], Albert, J [0000-0003-0253-2505], Albicocco, P [0000-0001-6430-1038], Verzini, MJA [0000-0003-2212-7830], Alderweireldt, S [0000-0002-8224-7036], Aleksa, M [0000-0002-1936-9217], Aleksandrov, IN [0000-0001-7381-6762], Alexa, C [0000-0003-0922-7669], Alexopoulos, T [0000-0002-8977-279X], Alfonsi, A [0000-0001-7406-4531], Alfonsi, F [0000-0002-0966-0211], Alhroob, M [0000-0001-7569-7111], Ali, B [0000-0001-8653-5556], Ali, S [0000-0001-5216-3133], Aliev, M [0000-0002-9012-3746], Alimonti, G [0000-0002-7128-9046], Allaire, C [0000-0003-4745-538X], Allbrooke, BMM [0000-0002-5738-2471], Allport, PP [0000-0001-7303-2570], Aloisio, A [0000-0002-3883-6693], Alonso, F [0000-0001-9431-8156], Alpigiani, C [0000-0002-7641-5814], Estevez, MA [0000-0002-8181-6532], Alviggi, MG [0000-0003-0026-982X], Coutinho, YA [0000-0002-1798-7230], Ambler, A [0000-0003-2184-3480], Ambroz, L [0000-0002-0987-6637], Amidei, D [0000-0002-6814-0355], Santos, SPAD [0000-0001-7566-6067], Amoroso, S [0000-0001-5450-0447], Amos, KR [0000-0003-1757-5620], Ananiev, V [0000-0003-3649-7621], Anastopoulos, C [0000-0003-1587-5830], Andari, N [0000-0002-4935-4753], Andeen, T [0000-0002-4413-871X], Anders, JK [0000-0002-1846-0262], Andrean, SY [0000-0002-9766-2670], Andreazza, A [0000-0001-5161-5759], Angelidakis, S [0000-0002-8274-6118], Angerami, A [0000-0001-7834-8750], Anisenkov, AV [0000-0002-7201-5936], Annovi, A [0000-0002-4649-4398], Antel, C [0000-0001-9683-0890], Anthony, MT [0000-0002-5270-0143], Antipov, E [0000-0002-6678-7665], Antonelli, M [0000-0002-2293-5726], Antrim, DJA [0000-0001-8084-7786], Anulli, F [0000-0003-2734-130X], Aoki, M [0000-0001-7498-0097], Pozo, JAA [0000-0001-7401-4331], Aparo, MA [0000-0003-4675-7810], Bella, LA [0000-0003-3942-1702], Aranzabal, N [0000-0001-9013-2274], Ferraz, VA [0000-0003-1177-7563], Arcangeletti, C [0000-0001-8648-2896], Arce, ATH [0000-0002-7255-0832], and Apollo - University of Cambridge Repository
Subjects: hep-ex, hep-ph
Abstract: This paper presents an analysis at next-to-next-to-leading order in the theory of quantum chromodynamics for the determination of a new set of proton parton distribution functions using diverse measurements in $pp$ collisions at $\sqrt{s} = 7$, 8 and 13 TeV, performed by the ATLAS experiment at the Large Hadron Collider, together with deep inelastic scattering data from $ep$ collisions at the HERA collider. The ATLAS data sets considered are differential cross-section measurements of inclusive $W^{\pm}$ and $Z/\gamma^*$ boson production, $W^{\pm}$ and $Z$ boson production in association with jets, $t\bar{t}$ production, inclusive jet production and direct photon production. In the analysis, particular attention is paid to the correlation of systematic uncertainties within and between the various ATLAS data sets and to the impact of model, theoretical and parameterisation uncertainties. The resulting set of parton distribution functions is called ATLASpdf21
Published: 2022

49. The ATLAS inner detector trigger performance in pp collisions at 13 TeV during LHC Run 2

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Achkar, B, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Adelman, J, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agapopoulou, C, Agaras, MN, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmad, A, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Akatsuka, S, Akbiyik, M, Åkesson, TPA, Akilli, E, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Ali, S, Aliev, M, Alimonti, G, Allaire, C, Allbrooke, BMM, Allport, PP, Aloisio, A, Alonso, F, Alpigiani, C, Camelia, EA, Estevez, MA, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amrouche, CS, Anastopoulos, C, Andari, N, Andeen, T, Anders, JK, Andrean, SY, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Aparo, MA, Bella, LA, Aranzabal, N, Ferraz, VA, Pereira, RA, Arcangeletti, C, Arce, ATH, Arguin, JF, Aad, G [0000-0002-6665-4934], Abbott, B [0000-0002-5888-2734], Abbott, DC [0000-0002-7248-3203], Abud, AA [0000-0002-2788-3822], Abeling, K [0000-0002-1002-1652], Abhayasinghe, DK [0000-0002-2987-4006], Abidi, SH [0000-0002-8496-9294], AbouZeid, OS [0000-0002-8279-9324], Abramowicz, H [0000-0001-5329-6640], Abreu, H [0000-0002-1599-2896], Abulaiti, Y [0000-0003-0403-3697], Acharya, BS [0000-0002-8588-9157], Achkar, B [0000-0002-0288-2567], Adam, L [0000-0001-6005-2812], Bourdarios, CA [0000-0002-2634-4958], Adamczyk, L [0000-0002-5859-2075], Adamek, L [0000-0003-1562-3502], Adelman, J [0000-0002-1041-3496], Adiguzel, A [0000-0001-6644-0517], Adorni, S [0000-0003-3620-1149], Adye, T [0000-0003-0627-5059], Affolder, AA [0000-0002-9058-7217], Afik, Y [0000-0001-8102-356X], Agapopoulou, C [0000-0002-2368-0147], Agaras, MN [0000-0002-4355-5589], Aggarwal, A [0000-0002-1922-2039], Agheorghiesei, C [0000-0003-3695-1847], Aguilar-Saavedra, JA [0000-0002-5475-8920], Ahmad, A [0000-0001-8638-0582], Ahmadov, F [0000-0003-3644-540X], Ahmed, WS [0000-0003-0128-3279], Ai, X [0000-0003-3856-2415], Aielli, G [0000-0002-0573-8114], Akatsuka, S [0000-0002-1681-6405], Akbiyik, M [0000-0002-7342-3130], Åkesson, TPA [0000-0003-4141-5408], Akilli, E [0000-0003-1309-5937], Akimov, AV [0000-0002-2846-2958], Khoury, KA [0000-0002-0547-8199], Alberghi, GL [0000-0003-2388-987X], Albert, J [0000-0003-0253-2505], Verzini, MJA [0000-0003-2212-7830], Alderweireldt, S [0000-0002-8224-7036], Aleksa, M [0000-0002-1936-9217], Aleksandrov, IN [0000-0001-7381-6762], Alexa, C [0000-0003-0922-7669], Alexopoulos, T [0000-0002-8977-279X], Alfonsi, A [0000-0001-7406-4531], Alfonsi, F [0000-0002-0966-0211], Alhroob, M [0000-0001-7569-7111], Ali, B [0000-0001-8653-5556], Ali, S [0000-0001-5216-3133], Aliev, M [0000-0002-9012-3746], Alimonti, G [0000-0002-7128-9046], Allaire, C [0000-0003-4745-538X], Allbrooke, BMM [0000-0002-5738-2471], Allport, PP [0000-0001-7303-2570], Aloisio, A [0000-0002-3883-6693], Alonso, F [0000-0001-9431-8156], Alpigiani, C [0000-0002-7641-5814], Estevez, MA [0000-0002-8181-6532], Alviggi, MG [0000-0003-0026-982X], Coutinho, YA [0000-0002-1798-7230], Ambler, A [0000-0003-2184-3480], Ambroz, L [0000-0002-0987-6637], Amidei, D [0000-0002-6814-0355], Santos, SPAD [0000-0001-7566-6067], Amoroso, S [0000-0001-5450-0447], Anastopoulos, C [0000-0003-1587-5830], Andari, N [0000-0002-4935-4753], Andeen, T [0000-0002-4413-871X], Anders, JK [0000-0002-1846-0262], Andrean, SY [0000-0002-9766-2670], Andreazza, A [0000-0001-5161-5759], Angelidakis, S [0000-0002-8274-6118], Angerami, A [0000-0001-7834-8750], Anisenkov, AV [0000-0002-7201-5936], Annovi, A [0000-0002-4649-4398], Antel, C [0000-0001-9683-0890], Anthony, MT [0000-0002-5270-0143], Antipov, E [0000-0002-6678-7665], Antonelli, M [0000-0002-2293-5726], Antrim, DJA [0000-0001-8084-7786], Anulli, F [0000-0003-2734-130X], Aoki, M [0000-0001-7498-0097], Pozo, JAA [0000-0001-7401-4331], Aparo, MA [0000-0003-4675-7810], Bella, LA [0000-0003-3942-1702], Aranzabal, N [0000-0001-9013-2274], Ferraz, VA [0000-0003-1177-7563], Arcangeletti, C [0000-0001-8648-2896], Arce, ATH [0000-0002-7255-0832], Arguin, JF [0000-0003-0229-3858], and Apollo - University of Cambridge Repository
Subjects: Physics::Instrumentation and Detectors, hep-ex, Physics::Accelerator Physics, High Energy Physics::Experiment
Abstract: The design and performance of the inner detector trigger for the high level trigger of the ATLAS experiment at the Large Hadron Collider during the 2016-18 data taking period is discussed. In 2016, 2017, and 2018 the ATLAS detector recorded 35.6 fb$^{-1}$, 46.9 fb$^{-1}$, and 60.6 fb$^{-1}$ respectively of proton-proton collision data at a centre-of-mass energy of 13 TeV. In order to deal with the very high interaction multiplicities per bunch crossing expected with the 13 TeV collisions the inner detector trigger was redesigned during the long shutdown of the Large Hadron Collider from 2013 until 2015. An overview of these developments is provided and the performance of the tracking in the trigger for the muon, electron, tau and $b$-jet signatures is discussed. The high performance of the inner detector trigger with these extreme interaction multiplicities demonstrates how the inner detector tracking continues to lie at the heart of the trigger performance and is essential in enabling the ATLAS physics programme.
Published: 2022

50. Direct constraint on the Higgs–charm coupling from a search for Higgs boson decays into charm quarks with the ATLAS detector

Author: Aad, G, Abbott, B, Abbott, DC, Abud, AA, Abeling, K, Abhayasinghe, DK, Abidi, SH, Aboulhorma, A, Abramowicz, H, Abreu, H, Abulaiti, Y, Hoffman, ACA, Acharya, BS, Achkar, B, Adam, L, Bourdarios, CA, Adamczyk, L, Adamek, L, Addepalli, SV, Adelman, J, Adiguzel, A, Adorni, S, Adye, T, Affolder, AA, Afik, Y, Agaras, MN, Agarwala, J, Aggarwal, A, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmad, A, Ahmadov, F, Ahmed, WS, Ai, X, Aielli, G, Aizenberg, I, Akbiyik, M, Åkesson, TPA, Akimov, AV, Khoury, KA, Alberghi, GL, Albert, J, Albicocco, P, Verzini, MJA, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alfonsi, A, Alfonsi, F, Alhroob, M, Ali, B, Ali, S, Aliev, M, Alimonti, G, Allaire, C, Allbrooke, BMM, Allport, PP, Aloisio, A, Alonso, F, Alpigiani, C, Camelia, EA, Estevez, MA, Alviggi, MG, Coutinho, YA, Ambler, A, Ambroz, L, Amelung, C, Amidei, D, Santos, SPAD, Amoroso, S, Amos, KR, Amrouche, CS, Ananiev, V, Anastopoulos, C, Andari, N, Andeen, T, Anders, JK, Andrean, SY, Andreazza, A, Angelidakis, S, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antipov, E, Antonelli, M, Antrim, DJA, Anulli, F, Aoki, M, Pozo, JAA, Aparo, MA, Bella, LA, Appelt, C, Aranzabal, N, Ferraz, VA, Arcangeletti, C, Arce, ATH, Aad, G [0000-0002-6665-4934], Abbott, B [0000-0002-5888-2734], Abbott, DC [0000-0002-7248-3203], Abud, AA [0000-0002-2788-3822], Abeling, K [0000-0002-1002-1652], Abhayasinghe, DK [0000-0002-2987-4006], Abidi, SH [0000-0002-8496-9294], Aboulhorma, A [0000-0002-9987-2292], Abramowicz, H [0000-0001-5329-6640], Abreu, H [0000-0002-1599-2896], Abulaiti, Y [0000-0003-0403-3697], Hoffman, ACA [0000-0003-0762-7204], Acharya, BS [0000-0002-8588-9157], Achkar, B [0000-0002-0288-2567], Adam, L [0000-0001-6005-2812], Bourdarios, CA [0000-0002-2634-4958], Adamczyk, L [0000-0002-5859-2075], Adamek, L [0000-0003-1562-3502], Addepalli, SV [0000-0002-2919-6663], Adelman, J [0000-0002-1041-3496], Adiguzel, A [0000-0001-6644-0517], Adorni, S [0000-0003-3620-1149], Adye, T [0000-0003-0627-5059], Affolder, AA [0000-0002-9058-7217], Afik, Y [0000-0001-8102-356X], Agaras, MN [0000-0002-4355-5589], Agarwala, J [0000-0002-4754-7455], Aggarwal, A [0000-0002-1922-2039], Agheorghiesei, C [0000-0003-3695-1847], Aguilar-Saavedra, JA [0000-0002-5475-8920], Ahmad, A [0000-0001-8638-0582], Ahmadov, F [0000-0003-3644-540X], Ahmed, WS [0000-0003-0128-3279], Ai, X [0000-0003-3856-2415], Aielli, G [0000-0002-0573-8114], Aizenberg, I [0000-0003-2150-1624], Akbiyik, M [0000-0002-7342-3130], Åkesson, TPA [0000-0003-4141-5408], Akimov, AV [0000-0002-2846-2958], Khoury, KA [0000-0002-0547-8199], Alberghi, GL [0000-0003-2388-987X], Albert, J [0000-0003-0253-2505], Albicocco, P [0000-0001-6430-1038], Verzini, MJA [0000-0003-2212-7830], Alderweireldt, S [0000-0002-8224-7036], Aleksa, M [0000-0002-1936-9217], Aleksandrov, IN [0000-0001-7381-6762], Alexa, C [0000-0003-0922-7669], Alexopoulos, T [0000-0002-8977-279X], Alfonsi, A [0000-0001-7406-4531], Alfonsi, F [0000-0002-0966-0211], Alhroob, M [0000-0001-7569-7111], Ali, B [0000-0001-8653-5556], Ali, S [0000-0001-5216-3133], Aliev, M [0000-0002-9012-3746], Alimonti, G [0000-0002-7128-9046], Allaire, C [0000-0003-4745-538X], Allbrooke, BMM [0000-0002-5738-2471], Allport, PP [0000-0001-7303-2570], Aloisio, A [0000-0002-3883-6693], Alonso, F [0000-0001-9431-8156], Alpigiani, C [0000-0002-7641-5814], Estevez, MA [0000-0002-8181-6532], Alviggi, MG [0000-0003-0026-982X], Coutinho, YA [0000-0002-1798-7230], Ambler, A [0000-0003-2184-3480], Ambroz, L [0000-0002-0987-6637], Amidei, D [0000-0002-6814-0355], Santos, SPAD [0000-0001-7566-6067], Amoroso, S [0000-0001-5450-0447], Amos, KR [0000-0003-1757-5620], Ananiev, V [0000-0003-3649-7621], Anastopoulos, C [0000-0003-1587-5830], Andari, N [0000-0002-4935-4753], Andeen, T [0000-0002-4413-871X], Anders, JK [0000-0002-1846-0262], Andrean, SY [0000-0002-9766-2670], Andreazza, A [0000-0001-5161-5759], Angelidakis, S [0000-0002-8274-6118], Angerami, A [0000-0001-7834-8750], Anisenkov, AV [0000-0002-7201-5936], Annovi, A [0000-0002-4649-4398], Antel, C [0000-0001-9683-0890], Anthony, MT [0000-0002-5270-0143], Antipov, E [0000-0002-6678-7665], Antonelli, M [0000-0002-2293-5726], Antrim, DJA [0000-0001-8084-7786], Anulli, F [0000-0003-2734-130X], Aoki, M [0000-0001-7498-0097], Pozo, JAA [0000-0001-7401-4331], Aparo, MA [0000-0003-4675-7810], Bella, LA [0000-0003-3942-1702], Appelt, C [0000-0003-1205-6784], Aranzabal, N [0000-0001-9013-2274], Ferraz, VA [0000-0003-1177-7563], Arcangeletti, C [0000-0001-8648-2896], Arce, ATH [0000-0002-7255-0832], and Apollo - University of Cambridge Repository
Subjects: Quantum Physics, Particle and Plasma Physics, Regular Article - Experimental Physics, hep-ex, Molecular, Nuclear, Atomic, Nuclear & Particles Physics
Abstract: A search for the Higgs boson decaying into a pair of charm quarks is presented. The analysis uses proton-proton collisions to target the production of a Higgs boson in association with a leptonically decaying $W$ or $Z$ boson. The dataset delivered by the LHC at a centre-of-mass energy of $\sqrt{s}=13$ TeV and recorded by the ATLAS detector corresponds to an integrated luminosity of 139 fb$^{-1}$. Flavour-tagging algorithms are used to identify jets originating from the hadronisation of charm quarks. The analysis method is validated with the simultaneous measurement of $WW,WZ$ and $ZZ$ production, with observed (expected) significances of $2.6$ ($2.2$) standard deviations above the background-only prediction for the $(W/Z)Z(\to c\bar{c})$ process and $3.8$ ($4.6$) standard deviations for the $(W/Z)W(\to cq)$ process. The $(W/Z)H(\to c \bar{c})$ search yields an observed (expected) upper limit of $26$ ($31$) times the predicted Standard Model cross-section times branching fraction for a Higgs boson with a mass of 125 GeV, corresponding to an observed (expected) constraint on the charm Yukawa coupling modifier $|\kappa_c| < 8.5 (12.4)$, at the 95% confidence level. A combination with the ATLAS $(W/Z)H, H\to b\bar{b}$ analysis is performed, allowing the ratio $\kappa_c / \kappa_b$ to be constrained without assumptions about the width of the Higgs boson. The ratio is constrained to be $|\kappa_c / \kappa_b| < 4.5$ at the 95% confidence level, smaller than the ratio of the $b$- and $c$-quark masses, and therefore determines the Higgs-charm coupling to be weaker than the Higgs-bottom coupling at the 95% confidence level.
Published: 2022

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