Georges Aad's research while affiliated with Aix-Marseille Université and other places

Publications (740)

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The accurate simulation of additional interactions at the ATLAS experiment for the analysis of proton–proton collisions delivered by the Large Hadron Collider presents a significant challenge to the computing resources. During the LHC Run 2 (2015–2018), there were up to 70 inelastic interactions per bunch crossing, which need to be accounted for in...
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During LHC Run 2 (2015–2018) the ATLAS Level-1 topological trigger allowed efficient data-taking by the ATLAS experiment at luminosities up to 2.1×1034 cm-2s-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 eve...
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The semiconductor tracker (SCT) is one of the tracking systems for charged particles in the ATLAS detector. It consists of 4088 silicon strip sensor modules. During Run 2 (2015–2018) the Large Hadron Collider delivered an integrated luminosity of 156 fb-1 to the ATLAS experiment at a centre-of-mass proton-proton collision energy of 13 TeV. The inst...
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The ATLAS experiment at the Large Hadron Collider (LHC) is operated at CERN and measures proton–proton collisions at multi-TeV energies with a repetition frequency of 40 MHz. Within the phase-II upgrade of the LHC, the readout electronics of the liquid-argon (LAr) calorimeters of ATLAS are being prepared for high luminosity operation expecting a pi...
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Measurements of both the inclusive and differential production cross sections of a top-quark–antiquark pair in association with a Z boson (tt¯Z) are presented. The measurements are performed by targeting final states with three or four isolated leptons (electrons or muons) and are based on s=13 TeV proton–proton collision data with an integrated lu...
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Jet energy scale and resolution measurements with their associated uncertainties are reported for jets using 36–81 fb-1 of proton–proton collision data with a centre-of-mass energy of s=13 TeV collected by the ATLAS detector at the LHC. Jets are reconstructed using two different input types: topo-clusters formed from energy deposits in calorimeter...
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Measurements of four-lepton differential and integrated fiducial cross-sections in events with two same-flavour, opposite-charge electron or muon pairs are presented. The data correspond to 139 fb−1 of s = 13 TeV proton-proton collisions, collected by the ATLAS detector during Run 2 of the Large Hadron Collider (2015–2018). The final state has cont...
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This article documents the muon reconstruction and identification efficiency obtained by the ATLAS experiment for 139 fb-1 of pp collision data at s=13 TeV collected between 2015 and 2018 during Run 2 of the LHC. The increased instantaneous luminosity delivered by the LHC over this period required a reoptimisation of the criteria for the identifica...
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This article presents a new set of proton parton distribution functions, ATLASepWZVjet20, produced in an analysis at next-to-next-to-leading order in QCD. The new data sets considered are the measurements of W+ and W− boson and Z boson production in association with jets in pp collisions at s = 8 TeV performed by the ATLAS experiment at the LHC wit...
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A search for pair production of third-generation scalar leptoquarks decaying into a top quark and a τ-lepton is presented. The search is based on a dataset of pp collisions at s = 13 TeV recorded with the ATLAS detector during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb−1. Events are selected if they have...
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A search for charged Higgs bosons decaying into a top quark and a bottom quark is presented. The data analysed correspond to 139 fb−1 of proton-proton collisions at s = 13 TeV, recorded with the ATLAS detector at the LHC. The production of a heavy charged Higgs boson in association with a top quark and a bottom quark, pp → tbH+ → tbtb, is explored...
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A search for charged Higgs bosons decaying into W±W± or W±Z bosons is performed, involving experimental signatures with two leptons of the same charge, or three or four leptons with a variety of charge combinations, missing transverse momentum and jets. A data sample of proton-proton collisions at a centre-of-mass energy of 13 TeV recorded with the...
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A search for new phenomena with top quark pairs in final states with one isolated electron or muon, multiple jets, and large missing transverse momentum is performed. Signal regions are designed to search for two-, three-, and four-body decays of the directly pair-produced supersymmetric partner of the top quark (stop). Additional signal regions ar...
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Several extensions of the Standard Model predict the production of dark matter particles at the LHC. An uncharted signature of dark matter particles produced in association with VV=W±W∓ or ZZ pairs from a decay of a dark Higgs boson s is searched for using 139 fb−1 of pp collisions recorded by the ATLAS detector at a center-of-mass energy of 13 TeV...
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The first measurement of longitudinal decorrelations of harmonic flow amplitudes vn for n=2–4 in Xe+Xe collisions at sNN=5.44 TeV is obtained using 3 μb−1 of data with the ATLAS detector at the LHC. The decorrelation signal for v3 and v4 is found to be nearly independent of collision centrality and transverse momentum (pT) requirements on final-sta...
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The yield of charged particles opposite to a Z boson with large transverse momentum (pT) is measured in 260 pb−1 of pp and 1.7 nb−1 of Pb+Pb collision data at 5.02 TeV per nucleon pair recorded with the ATLAS detector at the Large Hadron Collider. The Z boson tag is used to select hard-scattered partons with specific kinematics, and to observe how...
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The integrated fiducial cross-section and unfolded differential jet mass spectrum of high transverse momentum Z→bb‾ decays are measured in Zγ events in proton–proton collisions at s=13TeV. The data analysed were collected between 2015 and 2016 with the ATLAS detector at the Large Hadron Collider and correspond to an integrated luminosity of 36.1fb−...
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A search for the dimuon decay of the Standard Model (SM) Higgs boson is performed using data corresponding to an integrated luminosity of 139 fb−1 collected with the ATLAS detector in Run 2 pp collisions at s=13 TeV at the Large Hadron Collider. The observed (expected) significance over the background-only hypothesis for a Higgs boson with a mass o...
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A bstract Differential cross-sections are measured for top-quark pair production in the all-hadronic decay mode, using proton-proton collision events collected by the ATLAS experiment in which all six decay jets are separately resolved. Absolute and normalised single- and double-differential cross-sections are measured at particle and parton level...
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One correction is noted for the paper. A wrong cross-section was used for the theory prediction in figure 6 due to not taking into account the VHH contamination properly in the rescaling formula for the signal samples.
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The observation of forward proton scattering in association with lepton pairs (e+e−+p or μ+μ−+p) produced via photon fusion is presented. The scattered proton is detected by the ATLAS Forward Proton spectrometer, while the leptons are reconstructed by the central ATLAS detector. Proton-proton collision data recorded in 2017 at a center-of-mass ener...
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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 fb1, were recorded with the ATLAS detector from 2015 to 2018 at the Large Hadron Collider. The search is performed for final states in wh...
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A search for Higgs boson decays into a Z boson and a light resonance in two-lepton plus jet events is performed, using a pp collision dataset with an integrated luminosity of 139 fb−1 collected at s=13 TeV by the ATLAS experiment at the CERN LHC. The resonance considered is a light boson with a mass below 4 GeV from a possible extended scalar secto...
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In this paper, a new technique for reconstructing and identifying hadronically decaying τ+τ− pairs with a large Lorentz boost, referred to as the di-τ tagger, is developed and used for the first time in the ATLAS experiment at the Large Hadron Collider. A benchmark di-τ tagging selection is employed in the search for resonant Higgs boson pair produ...
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This paper presents a search for new heavy particles decaying into a pair of top quarks using 139 fb−1 of proton-proton collision data recorded at a centre-of-mass energy of s = 13 TeV with the ATLAS detector at the Large Hadron Collider. The search is performed using events consistent with pair production of high-transverse-momentum top quarks and...
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A bstract A search for a chargino-neutralino pair decaying via the 125 GeV Higgs boson into photons is presented. The study is based on the data collected between 2015 and 2018 with the ATLAS detector at the LHC, corresponding to an integrated luminosity of 139 fb − 1 of pp collisions at a centre-of-mass energy of 13 TeV. No significant excess over...
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A bstract Results of a search for new particles decaying into eight or more jets and moderate missing transverse momentum are presented. The analysis uses 139 fb − 1 of proton-proton collision data at $$ \sqrt{s} $$ s = 13 TeV collected by the ATLAS experiment at the Large Hadron Collider between 2015 and 2018. The selection rejects events containi...
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Figure 5b of the paper [1] contained a misinterpretation in the comparison between the reported new ATLAS measurement of the process pp → Xp and previously published CMS data [2]. The ATLAS measurement corresponds to cases where either proton dissociates.
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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...
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A bstract Inclusive and differential cross-sections for the production of top quarks in association with a photon are measured with proton-proton collision data corresponding to an integrated luminosity of 139 fb − 1 . The data were collected by the ATLAS detector at the LHC during Run 2 between 2015 and 2018 at a centre-of-mass energy of 13 TeV. T...
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A search for direct pair production of scalar partners of the top quark (top squarks or scalar third-generation up-type leptoquarks) in the all-hadronic \(t{\bar{t}}\) plus missing transverse momentum final state is presented. The analysis of 139 \(\hbox {fb}^{-1}\) of \({\sqrt{s}=13}\) TeV proton–proton collision data collected using the ATLAS det...
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A bstract The combination of measurements of the W boson polarization in top quark decays performed by the ATLAS and CMS collaborations is presented. The measurements are based on proton-proton collision data produced at the LHC at a centre-of-mass energy of 8 TeV, and corresponding to an integrated luminosity of about 20 fb − 1 for each experiment...
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A bstract The factor of four increase in the LHC luminosity, from 0 . 5 × 10 ³⁴ cm − 2 s − 1 to 2 . 0 × 10 ³⁴ cm − 2 s − 1 , and the corresponding increase in pile-up collisions during the 2015–2018 data-taking period, presented a challenge for the ATLAS trigger, particularly for those algorithms that select events with missing transverse momentum....
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The results of a search for electroweakino pair production \(pp \rightarrow \tilde{\chi }^\pm _1 \tilde{\chi }^0_2\) in which the chargino (\(\tilde{\chi }^\pm _1\)) decays into a W boson and the lightest neutralino (\(\tilde{\chi }^0_1\)), while the heavier neutralino (\(\tilde{\chi }^0_2\)) decays into the Standard Model 125 GeV Higgs boson and a...
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A search for heavy neutral Higgs bosons is performed using the LHC Run 2 data, corresponding to an integrated luminosity of 139 fb−1 of proton-proton collisions at s=13 TeV recorded with the ATLAS detector. The search for heavy resonances is performed over the mass range 0.2–2.5 TeV for the τ+τ− decay with at least one τ-lepton decaying into final...
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A bstract Single top-quark production in association with a Z boson, where the Z boson decays to a pair of charged leptons, is measured in the trilepton channel. The proton-proton collision data collected by the ATLAS experiment from 2015 to 2018 at a centre-of-mass energy of 13 TeV are used, corresponding to an integrated luminosity of 139 fb − 1...
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A bstract This paper presents a measurement of the production cross-section of a Z boson in association with b -jets, in proton-proton collisions at $$ \sqrt{s} $$ s = 13 TeV with the ATLAS experiment at the Large Hadron Collider using data corresponding to an integrated luminosity of 35.6 fb − 1 . Inclusive and differential cross-sections are meas...
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This paper describes precision measurements of the transverse momentum \(p_\mathrm {T}^{\ell \ell }\) (\(\ell =e,\mu \)) and of the angular variable \(\phi ^{*}_{\eta }\) 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 \(\sq...
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A bstract A search for Higgs boson pair production via vector-boson fusion (VBF) in the $$ b\overline{b}b\overline{b} $$ b b ¯ b b ¯ final state is carried out with the ATLAS experiment using 126 fb − 1 of proton- proton collision data delivered at $$ \sqrt{s} $$ s = 13 TeV by the Large Hadron Collider. This search is sensitive to VBF production of...
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The prevalence of hadronic jets at the LHC requires that a deep understanding of jet formation and structure is achieved in order to reach the highest levels of experimental and theoretical precision. There have been many measurements of jet substructure at the LHC and previous colliders, but the targeted observables mix physical effects from vario...
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A search for supersymmetric partners of gluons and quarks is presented, involving signatures with jets and either two isolated leptons (electrons or muons) with the same electric charge, or at least three isolated leptons. A data sample of proton-proton collisions at \( \sqrt{s} \) = 13 TeV recorded with the ATLAS detector at the Large Hadron Colli...
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The inclusive top quark pair (\(t\bar{t}\)) production cross-section \(\sigma _{t\bar{t}}\) has been measured in proton–proton collisions at \(\sqrt{s}=13\,\text {TeV}\), using 36.1 fb\(^{-1}\) of data collected in 2015–2016 by the ATLAS experiment at the LHC. Using events with an opposite-charge \(e\mu \) pair and b-tagged jets, the cross-section...
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A mistake was identified for the paper [1] in the treatment of the radion [2] cross-sections, which resulted in multiple changes.
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A search for dijet resonances in events with at least one isolated charged lepon is performed using 139 fb−1 of \( \sqrt{s} \) = 13 TeV proton-proton collision data recorded by the ATLAS detector at the LHC. The dijet invariant-mass (mjj) distribution constructed from events with at least one isolated electron or muon is searched in the region 0.22...
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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...
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A bstract A search for new resonances decaying into a pair of jets is reported using the dataset of proton-proton collisions recorded at $$ \sqrt{s} $$ s = 13 TeV with the ATLAS detector at the Large Hadron Collider between 2015 and 2018, corresponding to an integrated luminosity of 139 fb − 1 . The distribution of the invariant mass of the two lea...
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A bstract The production of a prompt photon in association with a Z boson is studied in proton-proton collisions at a centre-of-mass energy $$ \sqrt{s} $$ s = 13 TeV. The analysis uses a data sample with an integrated luminosity of 139 fb − 1 collected by the ATLAS detector at the LHC from 2015 to 2018. The production cross-section for the process...
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The production yield of Z bosons is measured in the electron and muon decay channels in Pb+Pb collisions at sNN=5.02 TeV with the ATLAS detector. Data from the 2015 LHC run corresponding to an integrated luminosity of 0.49 nb−1 are used for the analysis. The Z boson yield, normalised by the total number of minimum-bias events and the mean nuclear t...
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A bstract The dynamics of isolated-photon plus two-jet production in pp collisions at a centre-of-mass energy of 13 TeV are studied with the ATLAS detector at the LHC using a dataset corresponding to an integrated luminosity of 36 . 1 fb − 1 . Cross sections are measured as functions of a variety of observables, including angular correlations and i...
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The elliptic flow of muons from the decay of charm and bottom hadrons is measured in pp collisions at s=13 TeV using a data sample with an integrated luminosity of 150 pb−1 recorded by the ATLAS detector at the LHC. The muons from heavy-flavor decay are separated from light-hadron decay muons using momentum imbalance between the tracking and muon s...
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A bstract A dedicated sample of Large Hadron Collider proton-proton collision data at centre-of-mass energy $$ \sqrt{s} $$ s = 8 TeV is used to study inclusive single diffractive dissociation, pp → X p . The intact final-state proton is reconstructed in the ATLAS ALFA forward spectrometer, while charged particles from the dissociated system X are m...
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A search for magnetic monopoles and high-electric-charge objects is presented using 34.4 fb−1 of 13 TeV pp collision data collected by the ATLAS detector at the LHC during 2015 and 2016. The considered signature is based upon high ionization in the transition radiation tracker of the inner detector associated with a pencil-shape energy deposit in t...
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Multi-particle azimuthal cumulants are measured as a function of centrality and transverse momentum using 470 μb⁻¹ of Pb+Pb collisions at \( \sqrt{s_{\mathrm{NN}}} \) = 5.02 TeV with the ATLAS detector at the LHC. These cumulants provide information on the event-by-event fluctuations of harmonic flow coefficients vn and correlated fluctuations betw...
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A measurement of the production of a prompt J/ψ meson in association with a W± boson with W± → μν and J/ψ → μ⁺μ⁻ is presented for J/ψ transverse momenta in the range 8.5–150 GeV and rapidity |yJ/ψ| < 2.1 using ATLAS data recorded in 2012 at the LHC. The data were taken at a proton-proton centre-of-mass energy of \( \sqrt{s} \) = 8 TeV and correspon...
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Results are presented from the measurement by ATLAS of long-range (\(|\Delta \eta |>2\)) dihadron angular correlations in \(\sqrt{s}=8\) and 13 TeV pp collisions containing a Z boson. The analysis is performed using 19.4 \(\mathrm {fb}^{-1}\) of \(\sqrt{s}=8\) TeV data recorded during Run 1 of the LHC and 36.1 \(\mathrm {fb}^{-1}\) of \(\sqrt{s}=13...
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The azimuthal anisotropy of charged particles produced in \(\sqrt{s_{\mathrm {NN}}}=8.16\) TeV p+Pb collisions is measured with the ATLAS detector at the LHC. The data correspond to an integrated luminosity of 165 \(\mathrm {nb}^{-1}\) that was collected in 2016. Azimuthal anisotropy coefficients, elliptic \(v_2\) and triangular \(v_3\), extracted...
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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,...
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Measurements of \(K_S^0\) and \(\Lambda ^0\) production in \(t\bar{t}\) final states have been performed. They are based on a data sample with integrated luminosity of 4.6 \(\mathrm {fb}^{-1}\) 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 p...
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A bstract The result of a search for the pair production of the lightest supersymmetric partner of the bottom quark $$ \left({\tilde{b}}_1\right) $$ b ˜ 1 using 139 fb − 1 of proton-proton data collected at $$ \sqrt{s} $$ s = 13 TeV by the ATLAS detector is reported. In the supersymmetric scenarios considered both of the bottom-squarks decay into a...
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Abstract The production cross-sections for $$W^{\pm }$$ W± and Z bosons are measured using ATLAS data corresponding to an integrated luminosity of 4.0 pb$$^{-1}$$ -1 collected at a centre-of-mass energy $$\sqrt{s}=2.76$$ s=2.76 TeV. The decay channels $$W \rightarrow \ell \nu $$ W→ℓν and $$Z \rightarrow \ell \ell $$ Z→ℓℓ are used, where $$\ell $$ ℓ...