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41 papers found.
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Measurements of top-quark pair differential cross-sections in the \(e\mu \) channel in pp collisions at \(\sqrt{s} = 13\) TeV using the ATLAS detector

This article presents measurements of \(t\bar{t}\) differential cross-sections in a fiducial phase-space region, using an integrated luminosity of 3.2 fb\(^{-1}\) of proton–proton data at a centre-of-mass energy of \(\sqrt{s} = 13\) TeV recorded by the ATLAS experiment at the LHC in 2015. Differential cross-sections are measured as a function of the transverse momentum and absolute ...

Performance of the ATLAS trigger system in 2015

During 2015 the ATLAS experiment recorded \(3.8\,{\mathrm{fb}}^{-1}\) of proton–proton collision data at a centre-of-mass energy of \(13\,{\mathrm{TeV}}\). The ATLAS trigger system is a crucial component of the experiment, responsible for selecting events of interest at a recording rate of approximately 1 kHz from up to 40 MHz of collisions. This paper presents a short overview of ...

Reconstruction of primary vertices at the ATLAS experiment in Run 1 proton–proton collisions at the LHC

This paper presents the method and performance of primary vertex reconstruction in proton–proton collision data recorded by the ATLAS experiment during Run 1 of the LHC. The studies presented focus on data taken during 2012 at a centre-of-mass energy of \(\sqrt{s} = 8\) TeV. The performance has been measured as a function of the number of interactions per bunch crossing over a wide ...

Measurement of jet activity produced in top-quark events with an electron, a muon and two b-tagged jets in the final state in pp collisions at \(\sqrt{s}=13\) TeV with the ATLAS detector

Measurements of jet activity in top-quark pair events produced in proton–proton collisions are presented, using 3.2 fb\(^{-1}\) of pp collision data at a centre-of-mass energy of 13 TeV collected by the ATLAS experiment at the Large Hadron Collider. Events are chosen by requiring an opposite-charge \(e\mu \) pair and two b-tagged jets in the final state. The normalised differential ...

Measurement of the inclusive cross-sections of single top-quark and top-antiquark t-channel production in pp collisions at \( \sqrt{s}=13 \) TeV with the ATLAS detector

A measurement of the t-channel single-top-quark and single-top-antiquark production cross-sections in the lepton+jets channel is presented, using 3.2 fb−1 of proton-proton collision data at a centre-of-mass energy of 13 TeV, recorded with the ATLAS detector at the LHC in 2015. Events are selected by requiring one charged lepton (electron or muon), missing transverse momentum, and ...

Probing the W tb vertex structure in t-channel single-top-quark production and decay in pp collisions at \( \sqrt{s}=8 \) TeV with the ATLAS detector

To probe the W tb vertex structure, top-quark and W -boson polarisation observables are measured from t-channel single-top-quark events produced in proton-proton collisions at a centre-of-mass energy of 8 TeV. The dataset corresponds to an integrated luminosity of 20.2 fb−1, recorded with the ATLAS detector at the LHC. Selected events contain one isolated electron or muon, large ...

Measurement of the W boson polarisation in \(t\bar{t}\) events from pp collisions at \(\sqrt{s}\) = 8 TeV in the lepton + jets channel with ATLAS

This paper presents a measurement of the polarisation of W bosons from \(t\bar{t}\) decays, reconstructed in events with one high-\(p_{\text{ T }}\) lepton and at least four jets. Data from pp collisions at the LHC were collected at \(\sqrt{s}\) = 8 TeV and correspond to an integrated luminosity of 20.2 fb\(^{-1}\). The angle \(\theta ^{*}\) between the b-quark from the top quark ...

Search for new phenomena in events containing a same-flavour opposite-sign dilepton pair, jets, and large missing transverse momentum in \(\varvec{\sqrt{s}=13}\) \(\text {TeV}\) \(\varvec{pp}\) collisions with the ATLAS detector

Two searches for new phenomena in final states containing a same-flavour opposite-sign lepton (electron or muon) pair, jets, and large missing transverse momentum are presented. These searches make use of proton–proton collision data, collected during 2015 and 2016 at a centre-of-mass energy \(\sqrt{s}=13\) \(\text {TeV}\) by the ATLAS detector at the large hadron collider, which ...

Search for triboson \(W^{\pm }W^{\pm }W^{\mp }\) production in pp collisions at \(\sqrt{s}=8\) \(\text {TeV}\) with the ATLAS detector

This paper reports a search for triboson \(W^{\pm }W^{\pm }W^{\mp }\) production in two decay channels (\({W^{\pm }W^{\pm }W^{\mp } \rightarrow \ell ^\pm \nu \ell ^\pm \nu \ell ^\mp \nu }\) and \({W^{\pm }W^{\pm }W^{\mp } \rightarrow \ell ^\pm \nu \ell ^\pm \nu jj}\) with \(\ell =e, \mu \)) in proton-proton collision data corresponding to an integrated luminosity of 20.3 ...

Measurements of top quark spin observables in \( t\overline{t} \) events using dilepton final states in \( \sqrt{s}=8 \) TeV pp collisions with the ATLAS detector

Measurements of top quark spin observables in \( t\overline{t} \) events are presented based on 20.2 fb−1 of \( \sqrt{s}=8 \) TeV proton-proton collisions recorded with the ATLAS detector at the LHC. The analysis is performed in the dilepton final state, characterised by the presence of two isolated leptons (electrons or muons). There are 15 observables, each sensitive to a ...

Measurement of charged-particle distributions sensitive to the underlying event in \( \sqrt{s}=13 \) TeV proton-proton collisions with the ATLAS detector at the LHC

We present charged-particle distributions sensitive to the underlying event, measured by the ATLAS detector in proton-proton collisions at a centre-of-mass energy of 13 TeV, in low-luminosity Large Hadron Collider fills corresponding to an integrated luminosity of 1.6 nb−1. The distributions were constructed using charged particles with absolute pseudorapidity less than 2.5 and ...

Electron efficiency measurements with the ATLAS detector using 2012 LHC proton–proton collision data

This paper describes the algorithms for the reconstruction and identification of electrons in the central region of the ATLAS detector at the Large Hadron Collider (LHC). These algorithms were used for all ATLAS results with electrons in the final state that are based on the 2012 pp collision data produced by the LHC at \(\sqrt{\mathrm {s}}\) = 8 \(\text {TeV}\). The efficiency of ...

Measurement of the prompt J/ \(\psi \) pair production cross-section in pp collisions at \(\sqrt{s} = 8\) TeV with the ATLAS detector

The production of two prompt \(J/\psi \) mesons, each with transverse momenta \(p_{\mathrm {T}}>8.5\) GeV and rapidity \(|y| < 2.1\), is studied using a sample of proton-proton collisions at \(\sqrt{s} = 8\) TeV, corresponding to an integrated luminosity of 11.4 fb\(^{-1}\) collected in 2012 with the ATLAS detector at the LHC. The differential cross-section, assuming unpolarised ...

Measurements of charge and CP asymmetries in b-hadron decays using top-quark events collected by the ATLAS detector in pp collisions at \( \sqrt{s}=8 \) TeV

Same- and opposite-sign charge asymmetries are measured in lepton+jets \( t\overline{t} \) events in which a b-hadron decays semileptonically to a soft muon, using data corresponding to an integrated luminosity of 20.3 fb−1 from proton-proton collisions at a centre-of-mass energy of \( \sqrt{s}=8 \) TeV collected with the ATLAS detector at the Large Hadron Collider at CERN. The ...

Measurements of top-quark pair to Z-boson cross-section ratios at \( \sqrt{s}=13 \) , 8, 7 TeV with the ATLAS detector

Ratios of top-quark pair to Z-boson cross sections measured from proton-proton collisions at the LHC centre-of-mass energies of \( \sqrt{s}=13 \) TeV, 8 TeV, and 7 TeV are presented by the ATLAS Collaboration. Single ratios, at a given \( \sqrt{s} \) for the two processes and at different \( \sqrt{s} \) for each process, as well as double ratios of the two processes at different \( ...

A measurement of the calorimeter response to single hadrons and determination of the jet energy scale uncertainty using LHC Run-1 pp-collision data with the ATLAS detector

A measurement of the calorimeter response to isolated charged hadrons in the ATLAS detector at the LHC is presented. This measurement is performed with 3.2 nb\(^{-1}\) of proton–proton collision data at \(\sqrt{s}=7\) \(\,\mathrm{TeV}\) from 2010 and 0.1 nb\(^{-1}\) of data at \(\sqrt{s}=8\) \(\,\mathrm{TeV}\) from 2012. A number of aspects of the calorimeter response to isolated ...

Measurement of the \({\varvec{t\bar{t}Z}}\) and \({\varvec{t\bar{t}W}}\) production cross sections in multilepton final states using 3.2 fb \(^{-1}\) of \(\varvec{pp}\) collisions at \(\sqrt{s}\) = 13 TeV with the ATLAS detector

A measurement of the \(t\bar{t}Z\) and \(t\bar{t}W\) production cross sections in final states with either two same-charge muons, or three or four leptons (electrons or muons) is presented. The analysis uses a data sample of proton–proton collisions at \(\sqrt{s} = 13\) TeV recorded with the ATLAS detector at the Large Hadron Collider in 2015, corresponding to a total integrated ...

Measurement of the ZZ production cross section in proton-proton collisions at \( \sqrt{s}=8 \) TeV using the ZZ → ℓ−ℓ+ℓ′−ℓ′+ and \( ZZ\to {\ell}^{-}{\ell}^{+}\nu \overline{\nu} \) decay channels with the ATLAS detector

A measurement of the ZZ production cross section in the ℓ−ℓ+ℓ′ −ℓ′ + and \( {\ell}^{-}{\ell}^{+}\nu \overline{\nu} \) channels (ℓ = e, μ) in proton-proton collisions at \( \sqrt{s}=8 \)TeV at the Large Hadron Collider at CERN, using data corresponding to an integrated luminosity of 20.3 fb−1 collected by the ATLAS experiment in 2012 is presented. The fiducial cross sections for ZZ ...

Measurements of ψ(2S) and X(3872) → J/ψπ + π − production in pp collisions at \( \sqrt{s}=8 \) TeV with the ATLAS detector

Differential cross sections are presented for the prompt and non-prompt production of the hidden-charm states X(3872) and ψ(2S), in the decay mode J/ψπ + π −, measured using 11.4 fb−1 of pp collisions at \( \sqrt{s}=8 \) TeV by the ATLAS detector at the LHC. The ratio of cross-sections X(3872)/ψ(2S) is also given, separately for prompt and non-prompt components, as well as the ...

Luminosity determination in pp collisions at \(\sqrt{s}\) = 8 TeV using the ATLAS detector at the LHC

The luminosity determination for the ATLAS detector at the LHC during pp collisions at \(\sqrt{s} =\) 8 TeV in 2012 is presented. The evaluation of the luminosity scale is performed using several luminometers, and comparisons between these luminosity detectors are made to assess the accuracy, consistency and long-term stability of the results. A luminosity uncertainty of \(\delta ...