Search

We discuss significant improvements to our calculation of electroweak (EW) $t\bar{t}$ hadroproduction in extensions of the Standard Model (SM) with extra heavy neutral and charged spin-1 resonances using the Recola2 package. We allow for flavour-non-diagonal $Z'$ couplings and take into account non-resonant production in the SM and beyond including the contributions with t-channel $W$- and $W'$-bosons. We include next-to-leading order (NLO) QCD corrections and consistently match to parton showers with the POWHEG method fully taking into account the interference effects between SM and new physics amplitudes. We briefly describe the Contour method and give some information about the Rivet repository which catalogues particle-level measurements subsequently used by Contur to set limits on beyond the SM (BSM) theories. We explain how we use our calculation within Contour in order to set limits on models with additional heavy gauge bosons using LHC measurements, and illustrate this with an example using the leptophobic Topcolour (TC) model., 4 pages, 2 figures, contribution to the 2021 QCD session of the 55th Rencontres de Moriond

We critically (re)examine the associated production process of a $J/\psi$ meson plus an open charm hadron at the LHC in the proton-proton ($pp$) and proton-lead ($p{\rm Pb}$) collisions. Such a process is very intriguing in the sense of tailoring to explore the double parton structure of nucleons and to determine the geometry of partons in nuclei. In order to interpret the existing $pp$ data with the LHCb detector at the center-of-mass energy $\sqrt{s}=7$ TeV, we introduce two overlooked mechanisms for the double parton scattering (DPS) and single parton scattering (SPS) processes. Besides the conventional DPS mode, where the two mesons are produced almost independently in the two separate scattering subprocesses, we propose a novel DPS mechanism that the two constituent (heavy) quarks stemming from two hard scatterings can form into a composite particle, like the $J/\psi$ meson, during the hadronization phase. However, it turns out the corresponding contribution is small in $J/\psi+c\bar{c}$ hadroproduction. On the contrary, we point out that the resummation of the initial state logarithms due to gluon splitting into a charm quark pair is crucial to understand the LHCb measurement, which was overlooked in the literature. We perform a proper matching between the perturbative calculations in different initial-quark flavor number schemes, generically referring to the variable flavor number scheme. The new variable flavor number scheme calculation for the process strongly enhance the SPS cross sections, almost closing the discrepancies between theory and experiment. Finally, we present our predictions for the forthcoming LHCb measurement in $p{\rm Pb}$ collisions at $\sqrt{s_{NN}}=8.16$ TeV. Some interesting observables are exploited to set up the control regions of the DPS signal and to probe the impact-parameter dependent parton densities in lead., Comment: 32 pages, 20 figures, 7 tables; v2: match to journal version (add a new figure and a few references, fix a few typos)

After an introduction motivating the study of quarkonium production, we review the recent developments in the phenomenology of quarkonium production in inclusive scatterings of hadrons and leptons. We naturally address data and predictions relevant for the LHC, the Tevatron, RHIC, HERA, LEP, B factories and EIC. An up-to-date discussion of the contributions from feed downs within the charmonium and bottomonium families as well as from b hadrons to charmonia is also provided. This contextualises an exhaustive overview of new observables such as the associated production along with a Standard Model boson (photon, W and Z), with another quarkonium, with another heavy quark as well as with light hadrons or jets. We address the relevance of these reactions in order to improve our understanding of the mechanisms underlying quarkonium production as well as the physics of multi-parton interactions, in particular the double parton scatterings. An outlook towards future studies and facilities concludes this review., Comment: LaTeX, 151 pages; 71 figures, 13 tables. Version accepted for publication in Physics Reports

International audience; The precise knowledge of (anti-)neutrino fluxes is one of the largest limitation in accelerator-based neutrino experiments. The main limitations arise from the poorly known production properties of neutrino parents in hadron-nucleus interactions. Strategies used by neutrino experiment to constrain their fluxes using external hadroproduction data will be described and illustrated with an example of a tight collaboration between T2K and NA61/SHINE experiments. This enabled a reduction of the T2K neutrino flux uncertainty from ∼25% (without external constraints) down to ∼10%. On-going developments to further constrain the T2K (anti-)neutrino flux are discussed and recent results from NA61/SHINE are reviewed. As the next-generation long baseline experiments aim for a neutrino flux uncertainty at a level of a few percent, the future data-taking plans of NA61/SHINE are discussed.

This thesis addresses a study of the η c (1S) charmonium state using decays to proton-antiproton final state at the LHCb experiment. The production cross-section of the η c meson in parton interactions and in b-hadron decays are reported. Production of the η c (1S) state is measured via the decay to ppbar with the LHCb detector, using an integrated luminosity of 0.7 fb⁻¹ accumulated at 7 TeV centre-of-mass energy in 2011, and an integrated luminosity of 2 fb⁻¹ accumulated at 8 TeV centre-of-mass energy in 2012. The measurements are performed using the J/ψ → ppbar decay as a reference channel. High centre-of-mass energies available in proton-proton collisions at the LHC allow models describing charmonium production to be tested. We distinguish promptly produced charmonia from those originating from b-hadron decays. Promptly produced charmonia include charmonia directly produced in parton interactions and those originating from the decays of heavier quarkonium states, which are in turn produced in parton interactions. Prompt charmonium production comprises direct production in the parton interaction and charmonium originating from decays of heavier states. The relative rate of prompt production of the η c and J/ψ states in the LHCb acceptance (rapidity range 2.0 < y < 4.5) and for p T (J/ψ , η c ) > 6.5 GeV/c is measured for the first time to be σ (η c) /σ (J/ψ) = 1.74 ± 0.29 stat ± 0.28 syst ± 0.18 B at a centre-of-mass energy 7 TeV, and σ (η c) /σ (J/ψ) = 1.60 ± 0.29 stat ± 0.25 syst ± 0.17 B at a centre-of-mass energy s = 8 TeV. Using the J/ψ production cross-section measured by LHCb and assuming no J/ψ polarization, the absolute η c prompt production cross-section in the same kinematic regime is found to be σ η c = 0.52 ± 0.09 stat ± 0.08 syst ± 0.06 σ J/ψ , B at a centre-of-mass energy 7 TeV, and σ η c = 0.59 ± 0.11 stat ± 0.09 syst ± 0.08 σ J/ψ , B at a centre-of-mass energy s = 8 TeV. The third error component corresponds to the uncertainty in the J/ψ → pp and η c → pp branching fractions and the J/ψ cross-section measurement. The relative η c to J/ψ inclusive branching fraction from b-hadron decays is measured to be B(b→η c X) /B(b→J/ψ X) = 0.42 ± 0.06 stat ± 0.02 syst ± 0.05 B. Using the J/ψ inclusive branching fraction from b-hadron decays measured with the J/ψ → μμ decay channel, the inclusive η c branching fraction from b-hadron decays is found to be B(b→η c X) = (4.9 ± 0.6 stat ± 0.3 syst ± 0.7 B) × 10 ⁻³ ,where the third error component corresponds to the uncertainty in the J/ψ → pp and η c → pp branching fractions (and the J/ψ inclusive branching fraction from b-hadron decays). The measurement of the relative η c inclusive branching fraction from b-hadron decays is the most precise to date. Using low-background sample of η c from b-hadron decays, the J/ψ and η c mass difference, ∆M J/ψ , η c = 114.7 ± 1.5 ± 0.1 MeV/c² , is measured. The value of the relative inclusive η c production to J/ψ is important for distinguishing between a variety of theoretical models. The η c cross-section is measured in bins of transverse momentum. It exhibits a similar behaviour to those obtained in the J/ψ production analysis, though with significantly larger uncertainties. The upper limits on the production of some other charmonium states are addressed., Cette thèse répond une étude de la η c (1S) d'état de charmonium utilisant désintégrations à l'état final proton-antiproton à l'expérience LHCb. La section efficace de production du méson η c dans les interactions parton et dans les désintégrations b-hadrons sont signalés. La production de l'état η c (1S) est mesurée par la désintégration de ppbar avec le détecteur LHCb, en utilisant une luminosité intégrée de 0,7 fb⁻¹ accumulé à 7 TeV l'énergie de centre de masse en 2011, et une luminosité intégrée de 2 fb⁻¹ accumulé à 8 TeV l'énergie de centre de masse en 2012 les mesures sont effectuées en utilisant le J / ψ → ppbar décroissance comme un canal de référence. Haut de centre de masse des énergies disponibles dans les collisions proton-proton au LHC permet modèles décrivant la production de charmonium à tester. Nous distinguons rapidement présenté charmonia de ceux provenant de b-hadron se désintègre. Rapidement produites charmonia comprennent charmonia produit directement dans les interactions parton et ceux provenant de la désintégration de lourdes Etats quarkonium, qui sont à leur tour produit dans les interactions de partons. Production de charmonium invite comprend la production directe de l'interaction de parton et charmonium provenant de désintégrations des etats les plus lourds. Le taux relatif de la production rapide de l'etats η c et J / ψ dans l'acceptation LHCb (gamme de rapidité 2,0 6,5 GeV/c est mesurée pour la première le temps d'être σ (η c) / σ (J / ψ) = 1,74 ± 0,29 ± 0,28 stat syst ± 0,18 B l'énergie de centre de masse 7 TeV, et σ (η c) / σ (J / ψ) = 1,60 ± 0,29 stat ± 0,25 ± 0,17 syst B l'énergie de centre de masse 8 TeV. Utilisation du J / ψ section efficace de production mesurée par LHCb et en supposant qu'aucun J / ψ polarisation, l'absolu η c section efficace de production dans le même régime cinématique est σ η c = 0,52 ± 0,09 ± 0,08 stat syst ± 0,06 σ J / ψ, B l'énergie de centre de masse 7 TeV, et σ η c = 0,59 ± 0,11 stat ± 0,09 ± 0,08 syst σ J / ψ, B l'énergie de centre de masse 8 TeV. La troisième composante d'erreur correspond à l'incertitude de la J / ψ → p et η c → p ramification fractions et la mesure de section eficase J/ψ. Le rapport η c à J/ψ compris fraction de branchement de b-hadron désintégrations est mesuré pour être B (b → η c X) / B (b → J / ψ X) = 0,42 ± 0,06 ± 0,02 stat syst ± 0,05 B. Utilisation de l'J/ψ compris fraction ramification de b-hadron désintégrations mesuré avec le J/ψ →μμ canal de désintégration, l'inclusion η c ramification fraction de b-hadron désintégrations se trouve être B (b → η c X) = (4,9 ± 0,6 ± 0,3 stat syst ± 0,7 B) × 10 ⁻³, où la troisième composante d'erreur correspond à l'incertitude dans les J/ψ → pp et η c → pp ramification fractions (et le J/ψ compris fraction J ramification de b-hadron décroît). La mesure de la fraction η c de branchement inclus rapport de b-hadron se désintègre est la plus précise à ce jour. Utilisation de l'échantillon à faible fond de η c de b-hadron se désintègre, la différence de masse J / ψ et η c, ΔMJ / ψ, η c = 114,7 ± 1,5 ± 0,1 MeV / c², est mesurée. La valeur de la production par rapport compris η c J/ψ est important de faire la distinction entre une grande variété de modèles théoriques. Le η c section est mesurée dans des bacs de dynamique transversale. Il présente un comportement similaire à ceux obtenus dans l'analyse de la production J/ψ, mais avec beaucoup plus importantes incertitudes. Les limites supérieures sur la production de certains autres états charmonium sont adressées.