1,506 research outputs found

    Measurement of soft-drop jet observables in p p collisions with the ATLAS detector at s = 13TeV

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    Jet substructure quantities are measured using jets groomed with the soft-drop grooming procedure in dijet events from 32.9 fb−1 of pp collisions collected with the ATLAS detector at s=13 TeV. These observables are sensitive to a wide range of QCD phenomena. Some observables, such as the jet mass and opening angle between the two subjets which pass the soft-drop condition, can be described by a high-order (resummed) series in the strong coupling constant αS. Other observables, such as the momentum sharing between the two subjets, are nearly independent of αS. These observables can be constructed using all interacting particles or using only charged particles reconstructed in the inner tracking detectors. Track-based versions of these observables are not collinear safe, but are measured more precisely, and universal non-perturbative functions can absorb the collinear singularities. The unfolded data are directly compared with QCD calculations and hadron-level Monte Carlo simulations. The measurements are performed in different pseudorapidity regions, which are then used to extract quark and gluon jet shapes using the predicted quark and gluon fractions in each region. All of the parton shower and analytical calculations provide an excellent description of the data in most regions of phase space.Fil: Aad, G.. Aix-Marseille Université; FranciaFil: Abbott, B.. Ochanomizu University; JapónFil: Abbott, D. C.. University of Massachusetts; Estados UnidosFil: Abed Abud, A.. Cern - European Organization for Nuclear Research; SuizaFil: Abeling, K.. Georg August Universität Göttingen; AlemaniaFil: Abhayasinghe, D. K.. Royal Holloway University of London; Reino UnidoFil: Abidi, S. H.. University of Toronto; CanadáFil: AbouZeid, O. S.. University of Copenhagen; DinamarcaFil: Abraham, N. L.. University of Sussex; Reino UnidoFil: Abramowicz ,H.. Universitat Tel Aviv; IsraelFil: Abreu, H.. Technion - Israel Institute of Technology; IsraelFil: Abulaiti, Y.. Argonne National Laboratory; Estados UnidosFil: Acharya, B. S.. The Abdus Salam. International Centre for Theoretical Physics; Italia. Istituto Nazionale di Fisica Nucleare; ItaliaFil: Achkar, B.. Georg August Universität Göttingen; AlemaniaFil: Adachi,S.. University of Tokyo; JapónFil: Adam, L.. Technion - Israel Institute of Technology; IsraelFil: Adam Bourdarios, C.. Universite Grenoble Alpes; Francia. Université Savoie Mont Blanc; FranciaFil: Adamczyk, L.. AGH University of Science and Technology; PoloniaFil: Adamek, L.. University of Toronto; CanadáFil: Adelman, J.. Northern Illinois University; Estados UnidosFil: Adersberger, M.. Ludwig-Maximilians-Universität München; AlemaniaFil: Adiguzel, A.. Bahcesehir University; TurquíaFil: Adorni, S.. Université de Genève; SuizaFil: Adye, T.. Rutherford Appleton Laboratory; Reino UnidoFil: Affolder, A. A.. University of California Santa Cruz; Estados UnidosFil: Afik, Y.. Technion - Israel Institute of Technology; IsraelFil: Agapopoulou, C.. Universite Paris-Saclay; . Centre National de la Recherche Scientifique; FranciaFil: Agaras, M. N.. Université Clermont Auvergne; Francia. Centre National de la Recherche Scientifique; FranciaFil: Aggarwal, A.. Radboud Universiteit Nijmegen; Países BajosFil: Piegaia, Ricardo Nestor. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentin

    Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

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    This paper presents measurements of the W+μ+νW^+ \rightarrow \mu^+\nu and WμνW^- \rightarrow \mu^-\nu 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 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 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.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

    Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in √s=13 TeV pp collisions with the ATLAS detector

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    A search for supersymmetry through the pair production of electroweakinos with mass splittings near the electroweak scale and decaying via on-shell W and Z bosons is presented for a three-lepton final state. The analyzed proton-proton collision data taken at a center-of-mass energy of √s=13  TeV were collected between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 139  fb−1. A search, emulating the recursive jigsaw reconstruction technique with easily reproducible laboratory-frame variables, is performed. The two excesses observed in the 2015–2016 data recursive jigsaw analysis in the low-mass three-lepton phase space are reproduced. Results with the full data set are in agreement with the Standard Model expectations. They are interpreted to set exclusion limits at the 95% confidence level on simplified models of chargino-neutralino pair production for masses up to 345 GeV

    Gauge and Scheme Dependence of Mixing Matrix Renormalization

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    We revisit the issue of mixing matrix renormalization in theories that include Dirac or Majorana fermions. We show how a gauge-variant on-shell renormalized mixing matrix can be related to a manifestly gauge-independent one within a generalized MSˉ{\bar {\rm MS}} scheme of renormalization. This scheme-dependent relation is a consequence of the fact that in any scheme of renormalization, the gauge-dependent part of the mixing-matrix counterterm is ultra-violet safe and has a pure dispersive form. Employing the unitarity properties of the theory, we can successfully utilize the afore-mentioned scheme-dependent relation to preserve basic global or local symmetries of the bare Lagrangian through the entire process of renormalization. As an immediate application of our study, we derive the gauge-independent renormalization-group equations of mixing matrices in a minimal extension of the Standard Model with isosinglet neutrinos.Comment: 31 pages, LaTeX, uses axodraw.st

    Search for direct stau production in events with two hadronic tau-leptons in root s=13 TeV pp collisions with the ATLAS detector

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    A search for the direct production of the supersymmetric partners ofτ-leptons (staus) in final stateswith two hadronically decayingτ-leptons is presented. The analysis uses a dataset of pp collisions corresponding to an integrated luminosity of139fb−1, recorded with the ATLAS detector at the LargeHadron Collider at a center-of-mass energy of 13 TeV. No significant deviation from the expected StandardModel background is observed. Limits are derived in scenarios of direct production of stau pairs with eachstau decaying into the stable lightest neutralino and oneτ-lepton in simplified models where the two staumass eigenstates are degenerate. Stau masses from 120 GeV to 390 GeV are excluded at 95% confidencelevel for a massless lightest neutralino
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