Search

There are four fundamental forces within the natural world: electromagnetism, gravity, the strong nuclear force, and the weak nuclear force. One of the primary windows to the inner workings of the weak nuclear force has long been found in observations of beta decay processes. Of particular interest is the form taken by the couplings involved in beta decay; prior experiments have shown that the process is dominated by a combination of vector and axial couplings, analogous to Maxwell's theory of electromagnetism --- however the possibility of a non-dominant contribution from exotic scalar or tensor couplings remains. Such a discovery would shake the foundations upon which our understanding of the weak force is built. A precision kinematic measurement is conducted to search for- or constrain exotic couplings within the nuclear weak force by measuring an observable known as the Fierz interference, $b_{Fierz}$, within the $^{37}$K$ \rightarrow ^{37}$Ar$ + \beta^+ + \nu_e$ transition. The effect, if present, would manifest as a perturbation to the expected shape of the energy spectrum for betas emerging from a decay --- or equivalently, as an apparent change to the energy dependence of the beta asymmetry ($A_\beta$, measured with respect to nuclear polarization), which is the approach employed here. As the observable is comprised of a linear combination of scalar and tensor couplings, any non-zero value of $b_{Fierz}$ would be indicative of exotic physics. The measurement is carried out within the TRINAT laboratory located at TRIUMF, which provides the radioactive $^{37}$K necessary for the experiment. The TRINAT apparatus provides an isotope-specific means to cool, confine, and intermittently spin-polarize $^{37}$K atoms within a magneto-optical trap. Upon decay, outgoing particles are emitted from a small central cloud into an open geometry featuring a variety of detectors. A thorough understanding of the nuclear polarization allows the superratio technique to be employ

Construction of future Muon Collier (or dedicated µ-ring) tangential to the energy frontier hh colliders will give opportunity to realize µp and µA collisions at multi-TeV center-of-mass energies with sufficiently high luminosities. Obviously, such colliders will essentially enlarge the physics search potential of corresponding muon and hadron colliders for both the SM (especially for clarifying QCD basics and confinement hypothesis) and BSM phenomena. In addition, they will provide parton distribution functions for adequate interpretation of energy frontier hh colliders’ and cosmic ray experiments data. This paper is devoted to review of main parameters of µh colliders proposed until now. © World Scientific Publishing Company.

Construction of future Muon Collier (or dedicated µ-ring) tangential to the energy frontier hh colliders will give opportunity to realize µp and µA collisions at multi-TeV center-of-mass energies with sufficiently high luminosities. Obviously, such colliders will essentially enlarge the physics search potential of corresponding muon and hadron colliders for both the SM (especially for clarifying QCD basics and confinement hypothesis) and BSM phenomena. In addition, they will provide parton distribution functions for adequate interpretation of energy frontier hh colliders’ and cosmic ray experiments data. This paper is devoted to review of main parameters of µh colliders proposed until now. © World Scientific Publishing Company.

In The Standard Model, the coupling between the leptons and the gauge bosons is independent of the lepton generation. This is called Lepton Flavour Universality (LFU). This thesis aims to test LFU by studying two different processes involving D and B meson decays using data recorded by the LHCb experiment. The first LFU test aims to measure the branching fraction ratio R(mu/e)=BF(D0->Kmunu)/BF(D0- >Kenu). The result, which is still blinded, presents an uncertainty of 0.003(stat)±0.013(syst). The second LFU test is a simultaneous measurement of R(D0) and R(D*0), defined as BF(B->D(*)0taunu)/BF(B->D(*)0lnu), where (l=mu,e). This thesis presents a model implemented to study one of the main background components of this study, the inclusive Ds->3pi(X) decays, where the Ds decays in the tau decay vertex.

We report on a blinded analysis of low-energy electronic recoil data from the first science run of the XENONnT dark matter experiment. Novel subsystems and the increased 5.9 ton liquid xenon target reduced the background in the (1, 30) keV search region to (15.8±1.3) events/(ton×year×keV), the lowest ever achieved in a dark matter detector and ∼5 times lower than in XENON1T. With an exposure of 1.16 ton-years, we observe no excess above background and set stringent new limits on solar axions, an enhanced neutrino magnetic moment, and bosonic dark matter.

The aim of the proposed CERN Gamma Factory is to produce ≈1017 photons per second with energies up to 400 MeV. The photon beam intensity is expected to be a factor of (Formula presented.) larger than that of the presently available photon beams in the MeV energy range. In this work, its potential to probe physics beyond the Standard Model is explored. In particular, searches for axion like particles (ALPs) with dominant couplings to photons are discussed and various production scenarios—fixed target, photon–photon collision, and conversion by a magnetic field—and detection schemes considered—via decay to photons or back-conversion. It is found that the Gamma Factory in a fixed target mode can probe ALPs with mass (Formula presented.) and decay constants larger than 107 GeV, improving by an order of magnitude the discovery potential of previous beam dump experiments.

The Forward Physics Facility (FPF) is a proposal to create a cavern with the space and infrastructure to support a suite of far-forward experiments at the Large Hadron Collider during the High Luminosity era. Located along the beam collision axis and shielded from the interaction point by at least 100 m of concrete and rock, the FPF will house experiments that will detect particles outside the acceptance of the existing large LHC experiments and will observe rare and exotic processes in an extremely low-background environment. In this work, we summarize the current status of plans for the FPF, including recent progress in civil engineering in identifying promising sites for the FPF and the experiments currently envisioned to realize the FPF's physics potential. We then review the many Standard Model and new physics topics that will be advanced by the FPF, including searches for long-lived particles, probes of dark matter and dark sectors, high-statistics studies of TeV neutrinos of all three flavors, aspects of perturbative and non-perturbative QCD, and high-energy astroparticle physics.

The ATLAS detector at the Large Hadron Collider at CERN is used to search for the decay of a scalar boson to a pair of long-lived particles, neutral under the Standard Model gauge group, in 20.3 fb(-1) of data collected in proton-proton collisions at root s = 8 TeV. This search is sensitive to long-lived particles that decay to Standard Model particles producing jets at the outer edge of the ATLAS electromagnetic calorimeter or inside the hadronic calorimeter. No significant excess of events is observed. Limits are reported on the product of the scalar boson production cross section times branching ratio into long-lived neutral particles as a function of the proper lifetime of the particles. Limits are reported for boson masses from 100 GeV to 900 GeV, and a long-lived neutral particle mass from 10 GeV to 150 GeV. Published by Elsevier B.V.

Optomechanical systems can be used to probe weak forces arising from fundamental physical phenomena. Here, we analyze experimental efforts to search for ultralight dark matter and test spontaneous wave function collapse models, using ultra-low-loss micromechanical resonators based on silicon nitride membranes. We predict that constraints can be drawn in room temperature, table-top experiments that are competitive with the contemporary bounds set by large-scale experiments such as the Laser Interferometer Gravitational-Wave Observatory. In the future, we envision setting more stringent bounds by operating experiments in a cryostat.

The most important pillar in the physics case of future electron-positron colliders in high energy physics is the measurement of the Higgs boson, with its main goal to precisely measure its properties and to probe potential of associated new physics. All next generation electron positron facilities in high energy physics will make use of the Higgsstrahlung Higgs production channel. The physics potential of CEPC for measurement of the cross-section times branching ratio of subdominant decay H ? WW* is presented. The Higgsstrahnlung Higgs production channel is used, at the center of mass energy of 250 GeV. The fully hadronic decay, containing six soft-jets in the final state is of great importance for the detector design, jet pairing and reconstruction as showing the capability of CEPC for W/Z separation. The analysis is performed in full simulation. © Copyright owned by the author(s) under the terms of the Creative Commons

A search is made for massive highly ionising particles with lifetimes in excess of 100 ns, with the ATLAS experiment at the Large Hadron Collider, using 3.1 pb(-1) of pp collision data taken at root s = 7 TeV. The signature of energy loss in the ATLAS inner detector and electromagnetic calorimeter is used. No such particles are found and limits on the production cross section for electric charges 6e = vertical bar q vertical bar = 17e and masses 200 GeV = m = 1000 GeV are set in the range 1-12 pb for different hypotheses on the production mechanism. (C) 2011 CERN. Published by Elsevier B.V. All rights reserved.

A search for highly ionising, penetrating particles with electric charges from vertical bar q vertical bar = 2e to 6e is performed using the ATLAS detector at the CERN Large Hadron Collider. Proton-proton collision data taken at root s = 7 TeV during the 2011 running period, corresponding to an integrated luminosity of 4.4 fb(-1), are analysed. No signal candidates are observed, and 95% confidence level cross-section upper limits are interpreted as mass-exclusion lower limits for a simplified Drell-Yan production model. In this model, masses are excluded from 50 GeV up to 430, 480, 490, 470 and 420 GeV for charges 2e, 3e, 4e, 5e and 6e, respectively. (c) 2013 CERN. Published by Elsevier B.V. All rights reserved.

A search is made for massive highly ionising particles with lifetimes in excess of 100 ns, with the ATLAS experiment at the Large Hadron Collider, using 3.1 pb(-1) of pp collision data taken at root s = 7 TeV. The signature of energy loss in the ATLAS inner detector and electromagnetic calorimeter is used. No such particles are found and limits on the production cross section for electric charges 6e = vertical bar q vertical bar = 17e and masses 200 GeV = m = 1000 GeV are set in the range 1-12 pb for different hypotheses on the production mechanism. (C) 2011 CERN. Published by Elsevier B.V. All rights reserved.

Cette thèse présente une analyse de données collectées par le détecteur CMS, dont le but est la recherche de nouvelle physique dans des états finaux qui violent la conservation de la saveur leptonique. Elle commence avec une discussion du Modèle Standard de la physique des particules, en insistant sur la conservation de la saveur leptonique dans ce modèle, et sur la violation de cette conservation qui découle d’un grand nombre de modifications du Modèle Standard. Les problèmes non résolus en physique des particules sont présentés, ainsi que certains des modèles de nouvelle physique qui y répondent, et qui impliquent une violation de la conservation de la saveur leptonique. Nous discutons notamment la supersymétrie avec violation de la R-parité, des modèles avec des dimensions supplémentaires, et des modèles avec une symétrie de jauge U(1) supplémentaire. Ensuite, le LHC, le détecteur CMS, son système de déclenchement et son logiciel de reconstruction des événements sont tous décrits en détail. Les données analysées correspondent à une luminosité intégrée de 137 /fb collectée par CMS pendant trois années du Run 2 du LHC (2016-18), à une énergie du centre de masse √s = 13 TeV. La stratégie d’estimation du bruit de fond est de simuler tous les processus avec de vrais leptons dans l’état final, mais des méthodes basées sur les données sont utilisées pour les principaux bruits de fond où les leptons sont en fait des particules mal identifiées. Des facteurs de correction sont appliqués aux simulations afin de tenir compte d’effets expérimentaux et de calculs théoriques plus précis. Les données s’avèrent être compatibles avec les estimations du bruit de fond, en tenant compte des incertitudes, et une analyse statistique est faite afin d’exclure des modèles de nouvelle physique à un niveau de confiance de 95 %. Pour le modèle de référence, un boson Z’ avec des désintégrations qui ne conservent pas la saveur leptonique, les limites inférieures sur la masse de la résonance so, This thesis presents a novel search for new physics in lepton flavor violating final states, using the CMS detector. There is first a discussion of the Standard Model of particle physics, with a particular emphasis on the issue of lepton flavor conservation, and how often that conservation is violated when generic modifications of the Standard Model are performed. The questions left unanswered by the Standard Model are presented, as well as some new physics models which resolve them, and in so doing imply the existence of processes violating charged lepton flavor conservation. R-parity violating supersymmetry, models with large extra dimensions,and models with an extra U(1) gauge symmetry are discussed. The Large Hadron Collider, the CMS detector, its trigger system and event reconstruction software are all described in detail. The data used for the analysis corresponds to an integrated luminosity of 137 /fb collected by CMS during three years of LHC Run 2 (2016-18), at a center-of-mass energy √s = 13 TeV. The background estimation strategy is to use simulations for all processes with real leptons, while large-yield processes with misidentified leptons are estimated with data-driven methods. The simulations are corrected by scale factors accounting for experimental calibration and more precise theoretical calculations. After comparing the observed data and the expected background, no evidence of new physics is found, and a statistical analysis is performed to exclude new physics models at the 95 % confidence level. For the benchmark lepton flavor violating Z’ model, the lower limit in the eμ (respectively eτ ,μτ ) final state on the resonance mass is 5.0 TeV (resp. 4.2 TeV, 4.1 TeV). Such an analysis had never been performed in the tau channels with the CMS detector, and in all channels these results considerably improve on the previous state-of-the-art results., Doctorat en Sciences, info:eu-repo/semantics/nonPublished

This project has investigated the muon background of the SHiP experiment to determine whether it can boost the experiment sensitivity to visible Dark Photon decay. Using Fermi-Weizsäcker-Williams approximation to muon scattering we found the probability of muons generating massive photons, using Bremsstrahlung and direct lepton pair production as an estimation of the frequency of muon EM-interactions. In this work we only considered muons with momenta above 10 GeV/c. The number of visible Dark Photon decays was calculated for a range of the coupling constant and photon mass. The resulting range that promised visible decay has already been excluded by previous experiments, but the method could be used to further investigate enhanced production of Dark Photons from muons and electrons, and possibly also production of Axion-like particles. The work could also be used to estimate sensitivities of other experiments using muons.

We report on the first coherent excitation of the highly forbidden S21/2?F27/2 electric octupole (E3) transition in a single trapped Yb+172 ion, an isotope without nuclear spin. Using the transition in Yb+171 as a reference, we determine the transition frequency to be 642 116 784 950 887.6(2.4) Hz. We map out the magnetic field environment using the forbidden S21/2?D25/2 electric quadrupole (E2) transition and determine its frequency to be 729 476 867 027 206.8(4.4) Hz. Our results are a factor of 1×105 (3×105) more accurate for the E2 (E3) transition compared to previous measurements. The results open up the way to search for new physics via precise isotope shift measurements and improved tests of local Lorentz invariance using the metastable F27/2 state of Yb+. © 2020 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

A search for physics beyond the Standard Model (SM) is performed in events with final states including hadronic activity, missing energy, and significant momentum imbalance as measured with the MT2 variable. The results are based on data collected by the Compact Muon Solenoid detector at the Large Hadron Collider, and correspond to a total integrated luminosity of 35.9fb−1 of proton-proton collisions at a center-of-mass energy of 13TeV. No significant excess above the predicted SM background is observed. The results are interpreted as 95% confidence-level exclusion limits on the masses of hypothesized particles in a variety of simplified models of R-parity conserving supersymmetry (SUSY). Additional techniques for extending the search to target final states with low-momentum leptons is discussed, interpreted in in the context of SUSY models with compressed mass spectra, and compared to the exclusion strength of a typical all-hadronic search targeting such models.

The purpose of this study was to examine the life and work of vocal performer, teaching artist, and music educator JoAnn South Ottley (b. 1935), and trace her development from the early formative years through a successful singing and teaching career. This study is divided into a prologue, eleven chapters, and an epilogue. The chapter titles are as follows: Genealogy, Early Childhood, Childhood to Marriage, The Balancing Act, Building Foundations, Concentric Circles in Voice and Life, Paradigm Shift, Dissemination of the New Paradigm, LifeSong, and A Woman Interrupted. Raised by loving parents who resided in small ranching communities in Eastern Utah, JoAnn was unaware of the musical culture which would shape her career. She and her husband, Jerold Ottley received Fulbright Scholarships to study music in Germany. Afterward, JoAnn sang for symphonies and opera houses across the United States and internationally. Her teaching career began with private voice students, and eventually included teaching voice and related subjects as a music faculty member at the University of Utah and later Brigham Young University, Hawaii. JoAnn’s humble beginnings gave her a unique perspective as a singer and voice teacher in higher education. She noted issues of social injustice in the education and career possibilities for singers and observed a lack of balance in the lives of many performers. JoAnn taught with the intention to share the transformative nature of singing with her students, while encouraging them to live life fully. She identified the injustice inherent in university vocal education programs caused by unrealistic program goals to find the “one in a thousand” who might be able to succeed in the highly-competitive, specialized world of classical singing. She advocated for supporting and preparing “the other 999.” As a woman of faith, JoAnn worked to balance her life through a spiritual lens. As an autodidact, she studied diverse subjects. JoAnn made connections between al

Cosmic-ray (CR) particles propagating in the Galaxy interact in the interstellar medium with gas, losing energy and producing secondary particles via inelastic losses and fragmentation. Observations of the secondaries can be used to constrain the origin and propagation of the CRs, and may also provide signatures of new physics. To date CR propagation models have used the 2D Galactocentric cylindrical symmetry approximation for the spatial distribution of the interstellar gas. This is partly due to difficulties in uniquely determining its true 3D structure. In this contribution a method for determining the 3D spatial distribution of interstellar gas is described and first results using it to develop models that can be used in CR propagation codes like GALPROP are given. Implications for analysis of CR and γ-ray data using 3D spatial models for the interstellar gas are also discussed., QC 20181219

The physics of elementary particles is well described by the Standard Model of particle physics. This theory predicts with great accuracy the electroweak and strong interactions of elementary particles. The introduction of the Brout-Englert-Higgs mechanism in Standard Model has also given justification to the non-null mass of the elementary particles. This mechanism has been validated by the discovery of the Higgs boson and the measurement of its properties. Despite the enormous and broad success of the Standard Model, a few observations cannot be explained by this theory. For instance, neutrino oscillations would require the neutrinos to have non-null mass in contrast with the Standard Model prediction. Several solutions to this problem have been proposed, but none has been validated yet. Some of these theories have additional modes to produce lepton pairs with same electric charge (same-sign lepton pairs). This production is also expected to be enhanced in other theories beyond the Standard Model. The focus of this thesis is the inclusive search for anomalous production of same-sign lepton pairs in proton-proton collisions. The specific case of resonant production, typical of the Type-II see-saw and Zee-Babu models of neutrino mass generation, is also considered. 20.3/fb of data collected by the ATLAS experiment at a centre-of-mass energy of 8 TeV is analysed. No significant production above the Standard Model prediction is found, thus the results are used to set upper limits on the cross-section of processes beyond the Standard Model. Limits are placed as a function of the di-lepton invariant mass within a fiducial region defined according to the event selection criteria. Exclusion limits are also derived for specific models of resonant production. The production of same-sign lepton pairs from proton-proton collisions occurs rarely in the Standard Model. One process which generates same-sign lepton pairs is the associated production of a Higgs boson and a top ant

In this work, we examine how neutrino and collider experiments can each and together put constraints on new physics more stringently than ever. Constraints arise in three ways. First, possible new theoretical frameworks are reviewed and analyzed for the compatibility with collider experiments. We study alternate theories such as the superconnection formalism and non-commutative geometry (NCG) and show how these can be put to test, if any collider excess were to show up. In this case, we use the previous diboson and diphoton statistical excess as examples to do the analysis. Second, we parametrize low energy new physics in the neutrino sector in terms of non-standard interactions (NSI), which are constrained by past and proposed future neutrino experiments. As an example, we show the capability of resolving such NSI with the OscSNS, a detector proposed for Oak Ridge National Lab and derive interesting new constraints on NSI at very low energy (≲ 50 MeV). Apart from this, in order to better understand the NSI matter effect in long baseline experiments such as the future DUNE experiment, we derive a new compact formula to describe the effect analytically, which provides a clear physical picture of our understanding of the NSI matter effect compared to numerical computations. Last, we discuss the possibility of combining neutrino and collider data to get a better understanding of where the new physics is hidden. In particular, we study a model that produces sizable NSI to show how they can be constrained by past collider data, which covers a distinct region of the model parameter space from the DUNE experiment. In combining the two, we show that neutrino experiments are complementary to collider searches in ruling out models such as the ones that utilize a light mediator particle. More general procedures in constructing such models relevant to neutrino experiments are also described.

Mit dem Anstieg der Kollisionsenergie des LHC auf $13$TeV in Run 2 werden Ereignisse mit hohen Teilchendichten um ein Vielfaches häufiger. Im Zentrum hochenergetischer hadronischer Jets ist die durchschnittliche Entfernung zwischen geladenen Teilchen vergleichbar mit den Dimensionen der einzelnen Sensoren des ATLAS Inner Detector. Diese hohen Teilchendichten werden häufig durch Signaturen möglicher neuer Physik erzeugt, zum Beispiel massive Teilchen welche in stark geboostete Bosonen zerfallen. Diese hohe Dichte kann jedoch zu Problemen in der Spurenrekonstruktion führen. Durch gezielte Veränderungen der Spurenrekonstruktion können diese Probleme umgangen und deren Leistung verbessert werden. Solche Verbesserungen erhöhen sowohl die Chance neue Phänomene zu entdecken, als schaffen sie auch die Grundlage für detaillierte Messungen des neu erschlossenen kinematischen Regimes. Optimierungen der ATLAS Offline-Spurenrekonstruktion werden in dieser Arbeit erläutert und die daraus resultierende, verbesserte Leistung anhand von sowohl Monte-Carlo Simulation als auch von Daten präsentiert. Mit einer vollständig datenbasierte Methode wird jegliche verbleibende Ineffizienz der Spurenrekonstruktion im Zentrum von Jets als eine Funktion des Transversal-Impulses der Jets bestimmt. Der Bruchteil der Spuren welche einen Pixel-Cluster in der zweiten Pixel-Lage, erzeugt von zwei Teilchen, enthalten sollte und die bei der Rekonstruktion verloren gehen, wird mit Hilfe des Energieverlustes der Teilchen im Silizium bestimmt. Er variiert zwischen $0.061 \pm 0.006\textrm, With the increase in center-of-mass energy of the LHC to $\sqrt This work describes a series of improvements to the ATLAS offline track reconstruction to enhance its performance in dense environments. The effects of these improvements are demonstrated using both Monte Carlo simulation and data. Using data alone, residual inefficiencies of the track reconstruction in the core of jets are quantified as a function of the transverse momentum of the jet. The fraction of lost tracks is presented using the energy loss in silicon. It varies from $0.061 \pm 0.006\textrm It is demonstrated that combining the strengths of both the calorimeter and the tracker into a combined jet mass provides the most performant method currently, Roland Jansky, University of Innsbruck, Dissertation, 2016, OeBB, (VLID)1521637

The ATLAS detector at the Large Hadron Collider at CERN is used to search for the decay of a scalar boson to a pair of long-lived particles, neutral under the Standard Model gauge group, in 20.3 fb(-1) of data collected in proton-proton collisions at root s = 8 TeV. This search is sensitive to long-lived particles that decay to Standard Model particles producing jets at the outer edge of the ATLAS electromagnetic calorimeter or inside the hadronic calorimeter. No significant excess of events is observed. Limits are reported on the product of the scalar boson production cross section times branching ratio into long-lived neutral particles as a function of the proper lifetime of the particles. Limits are reported for boson masses from 100 GeV to 900 GeV, and a long-lived neutral particle mass from 10 GeV to 150 GeV., QC 20150814

The ATLAS detector at the Large Hadron Collider at CERN is used to search for the decay of a scalar boson to a pair of long-lived particles, neutral under the Standard Model gauge group, in 20.3fb-1 of data collected in proton-proton collisions at s=8TeV. This search is sensitive to long-lived particles that decay to Standard Model particles producing jets at the outer edge of the ATLAS electromagnetic calorimeter or inside the hadronic calorimeter. No significant excess of events is observed. Limits are reported on the product of the scalar boson production cross section times branching ratio into long-lived neutral particles as a function of the proper lifetime of the particles. Limits are reported for boson masses from 100 GeV to 900 GeV, and a long-lived neutral particle mass from 10 GeV to 150 GeV.

A search for heavy long-lived multi-charged particles is performed using the ATLAS detector at the LHC. Data collected in 2012 at [Formula: see text] TeV from pp collisions corresponding to an integrated luminosity of 20.3 fb[Formula: see text]are examined. Particles producing anomalously high ionisation, consistent with long-lived massive particles with electric charges from [Formula: see text] to [Formula: see text] are searched for. No signal candidate events are observed, and 95 % confidence level cross-section upper limits are interpreted as lower mass limits for a Drell-Yan production model. The mass limits range between 660 and 785 GeV.

The ATLAS detector at the Large Hadron Collider at CERN is used to search for the decay of a scalar boson to a pair of long-lived particles, neutral under the Standard Model gauge group, in 20.3 fb(-1) of data collected in proton-proton collisions at root s = 8 TeV. This search is sensitive to long-lived particles that decay to Standard Model particles producing jets at the outer edge of the ATLAS electromagnetic calorimeter or inside the hadronic calorimeter. No significant excess of events is observed. Limits are reported on the product of the scalar boson production cross section times branching ratio into long-lived neutral particles as a function of the proper lifetime of the particles. Limits are reported for boson masses from 100 GeV to 900 GeV, and a long-lived neutral particle mass from 10 GeV to 150 GeV.

The ATLAS detector at the Large Hadron Collider at CERN is used to search for the decay of a scalar boson to a pair of long-lived particles, neutral under the Standard Model gauge group, in 20.3 fb(-1) of data collected in proton-proton collisions at root s = 8 TeV. This search is sensitive to long-lived particles that decay to Standard Model particles producing jets at the outer edge of the ATLAS electromagnetic calorimeter or inside the hadronic calorimeter. No significant excess of events is observed. Limits are reported on the product of the scalar boson production cross section times branching ratio into long-lived neutral particles as a function of the proper lifetime of the particles. Limits are reported for boson masses from 100 GeV to 900 GeV, and a long-lived neutral particle mass from 10 GeV to 150 GeV. Published by Elsevier B.V.

The ATLAS detector at the Large Hadron Collider at CERN is used to search for the decay of a scalar boson to a pair of long-lived particles, neutral under the Standard Model gauge group, in 20.3 fb(-1) of data collected in proton-proton collisions at root s = 8 TeV. This search is sensitive to long-lived particles that decay to Standard Model particles producing jets at the outer edge of the ATLAS electromagnetic calorimeter or inside the hadronic calorimeter. No significant excess of events is observed. Limits are reported on the product of the scalar boson production cross section times branching ratio into long-lived neutral particles as a function of the proper lifetime of the particles. Limits are reported for boson masses from 100 GeV to 900 GeV, and a long-lived neutral particle mass from 10 GeV to 150 GeV. Published by Elsevier B.V.

In this review, we present highlight results of the first three years of the LHC running on searches for new physics beyond the Standard Model. The excellent performance of the LHC machine and detectors has provided a large, high-quality dataset, mainly proton-proton interactions at a centre of mass energy of 7 TeV (collected in 2010 and 2011) and 8 TeV (collected in 2012). This allowed the experiments to test the Standard Model at the highest available energy and to search for new phenomena in a considerably enlarged phase space compared to previous colliders., SCOPUS: sh.j, info:eu-repo/semantics/published

We discuss the possibilities of experimental search for the new physics predicted by the Gauss-Bonnet and the Randall-Sundrum theories of gravity. The effective four-dimensional spherically symmetrical solutions of these theories are analyzed. We consider these solutions in the weak-field limit and in the process of the primordial black hole evaporation. We show that the predictions of the discussed models are the same as of general relativity. Hence, current experiments are not applicable for such search, and therefore different methods of observation and higher accuracy are required. © 2015, Pleiades Publishing, Inc.

Numerous non-standard dynamics are described by contact-like effective interactions that can manifest themselves in e+e- collisions only through deviations of the observables (cross sections, asymme­tries) from the Standard Model predictions. If such a deviation were observed, it would be important to identify the actual source among the possible non-standard interactions as many different new physics scenarios may lead to very similar experimental signatures. Here we study the possibility of uniquely identifying the indirect effects of s-channel sneutrino exchange, as predicted by supersymmetric theories with R-parity violation, against other new physics scenarios in process e+e- — µ+µ- at the International Linear Col­lider. To evaluate the identification reach on sneutrino exchange, we use as basic observable a double polarization asymmetry, A doubie-Also, we examine the effects of neutrino and electron mixing with exotic heavy leptons in the process e+e- — W+W- within E6 models, in particular, the possibility of uniquely distinguishing and identifying such effects ofheavy neutral lepton exchange from Z —Z’ mixing.

Le sujet de la présente thèse porte sur la recherche de nouvelles particules très massives se désintégrant en une paire électron-positron avec le détecteur CMS.Le démarrage en 2010 du Large Hadron Collider au CERN marque le début d'une nouvelle ère en physique des particules. L'énergie et l'intensité de ses faisceaux de protons, inégalées à ce jour, offre en effet la possibilité d'étudier les lois décrivant les constituants ultimes de la matière et leurs interactions à des énergies jusqu'alors inaccessibles et d'étudier des processus rares. La découverte récente par les expériences ATLAS et CMS du boson scalaire prédit par la théorie de la brisure de symétrie électro-faible constitue ainsi la première percée du programme de recherche du LHC et confirme la théorie actuelle décrivant la physique subatomique, le Modèle Standard. Il est cependant largement admis que cette théorie, bien que hautement prédictive et jamais mise en défaut expérimentalement jusqu'à présent, ne constitue qu'une approximation à basse énergie d'une théorie plus fondamentale. Cette thèse décrit la recherche de nouvelles particules, prédites par plusieurs modèles au delà du Modèle Standard, via leur désintégration en une paire électron-positron de haute énergie. La reconstruction et la sélection des électrons de haute énergie par le détecteur CMS sont des éléments centraux de cette analyse et sont étudiées en détail. Divers critères sont développés afin de distinguer les électrons des autres types d'objets physiques produits lors de collisions de protons, tels que les jets. L'intensité des faisceaux du LHC est telle que plusieurs collisions ont lieu simultanément dans le détecteur et il est montré que l'efficacité de sélection des électrons dépend fortement du nombre de ces interactions. Une technique est donc mise au point pour corriger cet effet. Une méthode pour mesurer l'efficacité de la sélection directement sur les données est également développée. Celle-ci permet de confi, Doctorat en Sciences, info:eu-repo/semantics/nonPublished

Das Modell einer vierten Familie konnte bis heute aufgrund von theoretischen Argumenten nicht ausgeschlossen werden. In dieser Arbeit wird die Suche nach einem Down-artigen Quark der vierten Familie mit dem folgenden angenommenen Zerfall: pp -> b''b''bar+X -> t+W+tbar+W+X -> bbar+W+W+W+W+X vorgestellt. Für diese Analyse wird eine integrierte Luminosität von 2.05 fb−1 verwendet, aufgenommen mit dem ATLAS Experiment bei einer Schwerpunktsenergie von sqrt(s) = 7TeV für die Proton-Proton Kollisionen am Large Hadron Collider. In der Analyse werden Ereignisse mit zwei gleich geladenen Leptonen (e oder mu) in den Endzuständen selektiert, was eine seltene Signatur im Standard Modell darstellt. Neben einer verwendeten Standardselektierung für die Ereignisse, entnommen aus der ATLAS Top-Quark Analyse, wird eine Optimierung der Schnitte mit einer multivariaten Analyse durchgeführt. Des Weiteren werden systematische Unsicherheiten studiert, die durch die Partonendichteverteilungsfunktion sowie durch Abstrahlung von Teilchen wie Gluonen im Anfangs- und im Endzustand bei der Simulation mit dem Monte Carlo Generator entstehen. Mit den selektierten Ereignissen in der Signalregion von zwei gleich geladenen Leptonen wird durch eine Zählanalyse die Anzahl gemessener Signalereignisss extrahiert. Mit diesen Signalereignissen wird dann die untere Massenausschlussgrenze des b''-Quarks mit einer modifizierten Frequentistmethode bestimmt. Das Ergebnis zeigt, dass mit einem angenommenem Verzweigungsverhältnis von 100 % für den Zerfall b'' -> t + W alle Massen unterhalb einer Grenze von 461 GeV mit einem 95 % Konfidenzintervall ausgeschlossen sind., The model of a fourth generation is currently not excluded by theoretical arguments. In this thesis a search for a fourth generation down-type quark is presented with the decay hypothesis: pp -> b''b''bar+X -> t+W+tbar+W+X -> bbar+W+W+W+W+X The search is performed with an integrated luminosity of 2.05 fb−1 , obtained with the ATLAS experiment at the Large Hadron Collider running proton-proton collisions at a center-of-mass energy of sqrt(s) = 7TeV. Events for the analysis are selected with a search signature of two same-sign charged leptons (e or mu) in the final state, which is a rare Standard Model signature. Beside using the standard event selection from ATLAS top analyses, the event selection criteria are optimized with a multivariate analysis in order to maximize the significance. Furthermore, systematic uncertainties are studied coming from the parton distribution function as well as the initial and final state radiation. With the selected events in the signal region of two same-sign leptons, the signal is extracted via a counting method. The extracted signal is used for the determination of the mass limit of the fourth generation down-type quark with a modified frequentist method. Assuming a branching ratio of 100 % for the decay b'' -> t+W , b'' masses below 461 GeV are excluded at 95 % confidence level.

A search for highly ionising, penetrating particles with electric charges from vertical bar q vertical bar = 2e to 6e is performed using the ATLAS detector at the CERN Large Hadron Collider. Proton-proton collision data taken at root s = 7 TeV during the 2011 running period, corresponding to an integrated luminosity of 4.4 fb(-1), are analysed. No signal candidates are observed, and 95% confidence level cross-section upper limits are interpreted as mass-exclusion lower limits for a simplified Drell-Yan production model. In this model, masses are excluded from 50 GeV up to 430, 480, 490, 470 and 420 GeV for charges 2e, 3e, 4e, 5e and 6e, respectively., ATLAS Collaboration, for complete list of authors see http://dx.doi.org/10.1016/j.physletb.2013.04.036

A search for highly ionising, penetrating particles with electric charges from vertical bar q vertical bar = 2e to 6e is performed using the ATLAS detector at the CERN Large Hadron Collider. Proton-proton collision data taken at root s = 7 TeV during the 2011 running period, corresponding to an integrated luminosity of 4.4 fb(-1), are analysed. No signal candidates are observed, and 95% confidence level cross-section upper limits are interpreted as mass-exclusion lower limits for a simplified Drell-Yan production model. In this model, masses are excluded from 50 GeV up to 430, 480, 490, 470 and 420 GeV for charges 2e, 3e, 4e, 5e and 6e, respectively., AuthorCount:2898

A search for highly ionising, penetrating particles with electric charges from \q\=2e to 6e is performed using the ATLAS detector at the CERN Large Hadron Collider. Proton-proton collision data taken at √s=7TeV during the 2011 running period, corresponding to an integrated luminosity of 4.4fb-1, are analysed. No signal candidates are observed, and 95% confidence level cross-section upper limits are interpreted as mass-exclusion lower limits for a simplified Drell-Yan production model. In this model, masses are excluded from 50GeV up to 430, 480, 490, 470 and 420GeV for charges 2e, 3e, 4e, 5e and 6e, respectively. © 2013 CERN.

A search for highly ionising, penetrating particles with electric charges from vertical bar q vertical bar = 2e to 6e is performed using the ATLAS detector at the CERN Large Hadron Collider. Proton-proton collision data taken at root s = 7 TeV during the 2011 running period, corresponding to an integrated luminosity of 4.4 fb(-1), are analysed. No signal candidates are observed, and 95% confidence level cross-section upper limits are interpreted as mass-exclusion lower limits for a simplified Drell-Yan production model. In this model, masses are excluded from 50 GeV up to 430, 480, 490, 470 and 420 GeV for charges 2e, 3e, 4e, 5e and 6e, respectively. (c) 2013 CERN. Published by Elsevier B.V. All rights reserved.

A search is made for massive highly ionising particles with lifetimes in excess of 100 ns, with the ATLAS experiment at the Large Hadron Collider, using 3.1 pb(-1) of pp collision data taken at root s = 7 TeV. The signature of energy loss in the ATLAS inner detector and electromagnetic calorimeter is used. No such particles are found and limits on the production cross section for electric charges 6e <= vertical bar q vertical bar <= 17e and masses 200 GeV <= m <= 1000 GeV are set in the range 1-12 pb for different hypotheses on the production mechanism.

A search is made for massive highly ionising particles with lifetimes in excess of 100 ns, with the ATLAS experiment at the Large Hadron Collider, using 3.1 pb-1 of pp collision data taken at √s=7 TeV. The signature of energy loss in the ATLAS inner detector and electromagnetic calorimeter is used. No such particles are found and limits on the production cross section for electric charges 6e≤|q|≤17e and masses 200 GeV≤m≤1000 GeV are set in the range 1-12 pb for different hypotheses on the production mechanism. © 2011 CERN.

We perform a search for long-lived neutral particles decaying into a photon and invisible particles in pp collisions at a center-of-mass energy of 7 TeV at the Large Hadron Collider. In the context of gauge mediated supersymmetry with the lightest neutralino as the next-to-lightest supersymmetric particle and the gravitino as the lightest supersymmetric particle, the neutralino can decay into a gravitino and a photon with a non-zero lifetime. The impact parameter of the photon relative to the beam-beam collision point can be reconstructed using converted photons. The method is sensitive to lifetimes of the order of $\mathcal{O}$(0.1 ns). The data sample corresponds to an integrated luminosity of $2.1 \pm 0.1~\rm{fb^{-1}}$ recorded in the first part of 2011 by the CMS experiment at the LHC at $\sqrt{s}$ = 7 TeV. The search is performed using events containing photons, missing transverse energy and jets. Upper limits at the $\rm{95\%}$ confidence level are presented on the cross section for such particles from pair-production, each of which decays into a photon and invisible particles.

A search is made for massive highly ionising particles with lifetimes in excess of 100 ns, with the ATLAS experiment at the Large Hadron Collider, using 3.1 pb-1 of pp collision data taken at √s=7 TeV. The signature of energy loss in the ATLAS inner detector and electromagnetic calorimeter is used. No such particles are found and limits on the production cross section for electric charges 6e≤\q\≤17e and masses 200 GeV≤m≤1000 GeV are set in the range 1-12 pb for different hypotheses on the production mechanism. © 2011 CERN.

A search is made for massive highly ionising particles with lifetimes in excess of 100 ns, with the ATLAS experiment at the Large Hadron Collider, using 3.1 pb-1 of pp collision data taken at √s=7 TeV. The signature of energy loss in the ATLAS inner detector and electromagnetic calorimeter is used. No such particles are found and limits on the production cross section for electric charges 6e≤\q\≤17e and masses 200 GeV≤m≤1000 GeV are set in the range 1-12 pb for different hypotheses on the production mechanism. © 2011 CERN.

A search is made for massive highly ionising particles with lifetimes in excess of 100 ns, with the ATLAS experiment at the Large Hadron Collider, using 3.1 pb(-1) of pp collision data taken at root s = 7 TeV. The signature of energy loss in the ATLAS inner detector and electromagnetic calorimeter is used. No such particles are found and limits on the production cross section for electric charges 6e LT = vertical bar q vertical bar LT = 17e and masses 200 GeV LT = m LT = 1000 GeV are set in the range 1-12 pb for different hypotheses on the production mechanism. (C) 2011 CERN. Published by Elsevier B.V. All rights reserved.

Cette thèse a été réalisée dans le cadre du LHC (Large Hadron Collider). Le LHC produit des collisions proton-proton avec une énergie dans le centre de masse de 7 TeV au CERN depuis mars 2010. C'est le collisionneur doté de la plus grande énergie dans le centre de masse et de la plus grande intensité de faisceaux jamais construit ;ce qui permet de pouvoir rechercher des processus physiques très rares associés à des énergies encore jamais atteintes. L'expérience CMS (Compact Muon Solenoid), au LHC, est un détecteur généraliste pour de nombreuses études de physique. CMS va fournir un outil très précieux pour tester la physique à l'échelle du TeV. Il possède des caractéristiques qui en font un excellent détecteur pour la reconstruction et la mesure des leptons.Le Modèle Standard de la physique des particules élementaires décrit les particules élementaires et trois des quatre interactions fondamentales (l'électromagnétisme, la force faible et la force forte). La volonté de décrire les quatre forces fondamentales en une seule et même théorie, ainsi que des insuffisances du Modèle Standard, ont mené les physiciens à élaborer de nouvelles approches théoriques. Plusieurs de ces théories prédisent l'existence de nouveaux bosons massifs, pouvant se désintégrer en une paire de leptons chargés. L'objet de cette thèse est la recherche de tels bosons massifs se désintégrant en une paire ee ou e-mu dans le détecteur CMS, en utilisant les données prises au LHC en 2010 (35 pb-1) et en 2011 (3.35 fb-1).A priori, les canaux dileptoniques sont appropriés pour rechercher des signaux de nouvelle physique dans la phase de démarrage d'un collisionneur hadronique. Néanmoins, il est important de vérifier que la réponse du détecteur, décrite par les simulations détaillées de celui-ci, est conforme aux attentes. Ceci constitue une partie importante de ma thèse. J'ai mis en évidence au cours de ce travail, au moyen de simulations par Monte Carlo, que le processus t-tbar contri, Doctorat en Sciences, info:eu-repo/semantics/nonPublished