955 research outputs found
Optimization of RPCs read-out panel with electromagnetic simulation
With the upgrade of the RPCs [1]-[2] and the increase of its performances,
the study and the optimization of the read-out panel is necessary in order to
maintain the signal integrity and to reduce the intrinsic crosstalk. Through
Electromagnetic Simulation, performed with CST Studio Suite, new panels design
are tested and their crosstalk property are studied. The behavior of different
type of panel is shown, in particular a panel with the decoupling strip
connected through their characteristic impedance to the ground plane is
simulated
Search for third-generation vector-like leptons in pp collisions at ās = 13 TeV with the ATLAS detector
A search for vector-like leptons in multilepton (two, three, or four-or-more electrons plus muons) final states with zero or more hadronic Ļ-lepton decays is presented. The search is performed using a dataset corresponding to an integrated luminosity of 139 fbā1 of proton-proton collisions at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector at the LHC. To maximize the separation of signal and background, a machine-learning classifier is used. No excess of events is observed beyond the Standard Model expectation. Using a doublet vector-like lepton model, vector-like leptons coupling to third-generation Standard Model leptons are excluded in the mass range from 130 GeV to 900 GeV at the 95% confidence level, while the highest excluded mass is expected to be 970 GeV. [Figure not available: see fulltext.]
Production of Ļ(nS) mesons in Pb + Pb and pp collisions at 5.02 TeV
A measurement of the production of vector bottomonium states, Ļ(1S), Ļ(2S), and Ļ(3S), in Pb + Pb and pp collisions at a center-of-mass energy per nucleon pair of 5.02 TeV is presented. The data correspond to integrated luminosities of 1.38 nb-1 of Pb + Pb data collected in 2018, 0.44 nb-1 of Pb + Pb data collected in 2015, and 0.26 fb-1 of pp data collected in 2017 by the ATLAS detector at the Large Hadron Collider. The measurements are performed in the dimuon decay channel for transverse momentum pĪ¼Ī¼T < 30 GeV, absolute rapidity |yĪ¼Ī¼| < 1.5, and Pb + Pb event centrality 0-80%. The production rates of the three bottomonium states in Pb + Pb collisions are compared with those in pp collisions to extract the nuclear modification factors as functions of event centrality, pĪ¼Ī¼T, and |yĪ¼Ī¼|. In addition, the suppression of the excited states relative to the ground state is studied. The results are compared with theoretical model calculations
Measurement of the Higgs boson mass in the H ā Z Zā ā 4 decay channel using 139 fbā1 of ās = 13 TeV pp collisions recorded by the ATLAS detector at the LHC
The mass of the Higgs boson is measured in the HāZZāā4ā decay channel. The analysis uses protonāproton collision data from the Large Hadron Collider at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector between 2015 and 2018, corresponding to an integrated luminosity of 139 fbā1. The measured value of the Higgs boson mass is 124.99Ā±0.18(stat.)Ā±0.04(syst.) GeV. In final states with muons, this measurement benefits from an improved momentum-scale calibration relative to that adopted in previous publications. The measurement also employs an analytic model that takes into account the invariant-mass resolution of the four-lepton system on a per-event basis and the output of a deep neural network discriminating signal from background events. This measurement is combined with the corresponding measurement using 7 and 8 TeV pp collision data, resulting in a Higgs boson mass of 124.94Ā±0.17(stat.)Ā±0.03(syst.) GeV
Cross-section measurements for the production of a Z boson in association with high-transverse-momentum jets in pp collisions at ās = 13 TeV with the ATLAS detector
Cross-section measurements for a Z boson produced in association with high-transverse-momentum jets (p T ā„ 100 GeV) and decaying into a charged-lepton pair (e + e ā , Ī¼ + Ī¼ ā) are presented. The measurements are performed using protonāproton collisions at s = 13 TeV corresponding to an integrated luminosity of 139 fb ā1 collected by the ATLAS experiment at the LHC. Measurements of angular correlations between the Z boson and the closest jet are performed in events with at least one jet with p T ā„ 500 GeV. Event topologies of particular interest are the collinear emission of a Z boson in dijet events and a boosted Z boson recoiling against a jet. Fiducial cross sections are compared with state-of-the-art theoretical predictions. The data are found to agree with next-to-next-to-leading-order predictions by NNLOjet and with the next-to-leading-order multi-leg generators MadGraph5_aMC@NLO and Sherpa. [Figure not available: see fulltext.]
Search for new phenomena in multi-body invariant masses in events with at least one isolated lepton and two jets using ās = 13 TeV protonāproton collision data collected by the ATLAS detector
A search for resonances in events with at least one isolated lepton (e or Ī¼) and two jets is performed using 139 fb ā1 of s = 13 TeV protonāproton collision data recorded by the ATLAS detector at the LHC. Deviations from a smoothly falling background hypothesis are tested in three- and four-body invariant mass distributions constructed from leptons and jets, including jets identified as originating from bottom quarks. Model-independent limits on generic resonances characterised by cascade decays of particles leading to multiple jets and leptons in the final state are presented. The limits are calculated using Gaussian shapes with different widths for the invariant masses. The multi-body invariant masses are also used to set 95% confidence level upper limits on the cross-section times branching ratios for the production and subsequent decay of resonances predicted by several new physics scenarios. [Figure not available: see fulltext.]
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