@article{OPUS4-17335,
  title     = {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},
  series = {Journal of High Energy Physics},
  volume    = {2017},
  journal   = {Journal of High Energy Physics},
  number    = {04},
  organization    = {The ATLAS Collaboration},
  doi       = {https://doi.org/10.1007/JHEP04(2017)086},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-173357},
  year      = {2017},
  abstract  = {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 two jets with high transverse momentum, exactly one of which is required to be \(b\)-tagged. Using a binned maximum-likelihood fit to the discriminant distribution of a neural network, the cross-sections are determined to be \({σ(tq)}\) = 156 ± 5 (stat.) ± 27 (syst.) ± 3 (lumi.) pb for single top-quark production and \(σ(\overline{t}q)\) = 91 ± 4 (stat.) ± 18 (syst.) ± 2 (lumi.) pb for single top-antiquark production, assuming a top-quark mass of 172.5 GeV. The cross-section ratio is measured to be \(R_{t}\) = \(σ(tq)/σ(\overline{t}q)\) = 1.72 ± 0.09 (stat.) ± 0.18 (syst.). All results are in agreement with Standard Model predictions.},
  language  = {en}
}
@article{OPUS4-17336,
  title     = {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},
  series = {Journal of High Energy Physics},
  volume    = {2017},
  journal   = {Journal of High Energy Physics},
  number    = {03},
  organization    = {The ATLAS Collaboration},
  doi       = {https://doi.org/10.1007/JHEP03(2017)157},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-173361},
  year      = {2017},
  abstract  = {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 with transverse momentum greater than 500 MeV, in events with at least one such charged particle with transverse momentum above 1 GeV. These distributions characterise the angular distribution of energy and particle flows with respect to the charged particle with highest transverse momentum, as a function of both that momentum and of charged-particle multiplicity. The results have been corrected for detector effects and are compared to the predictions of various Monte Carlo event generators, experimentally establishing the level of underlying-event activity at LHC Run 2 energies and providing inputs for the development of event generator modelling. The current models in use for UE modelling typically describe this data to 5\% accuracy, compared with data uncertainties of less than 1\%.},
  language  = {en}
}
@article{OPUS4-17278,
  title     = {Search for supersymmetry in final states with two same-sign or three leptons and jets using 36 fb\(^{-1}\) of \(\sqrt{s}=13\) TeV \(pp\) collision data with the ATLAS detector},
  series = {Journal of High Energy Physics},
  volume    = {2017},
  journal   = {Journal of High Energy Physics},
  number    = {09},
  organization    = {The ATLAS Collaboration},
  doi       = {https://doi.org/10.1007/JHEP09(2017)084},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-172787},
  year      = {2017},
  abstract  = {A search for strongly produced supersymmetric particles using signatures involving multiple energetic jets and either two isolated same-sign leptons (\(e\) or \(µ\)), or at least three isolated leptons, is presented. The analysis relies on the identification of \(b\)-jets and high missing transverse momentum to achieve good sensitivity. A data sample of proton-proton collisions at \(\sqrt{s} = 13\) TeV recorded with the ATLAS detector at the Large Hadron Collider in 2015 and 2016, corresponding to a total integrated luminosity of 36.1 fb\(^{-1}\), is used for the search. No significant excess over the Standard Model prediction is observed. The results are interpreted in several simplified supersymmetric models featuring \(R\)-parity conservation or \(R\)-parity violation, extending the exclusion limits from previous searches. In models considering gluino pair production, gluino masses are excluded up to 1.87 TeV at 95\% confidence level. When bottom squarks are pair-produced and decay to a chargino and a top quark, models with bottom squark masses below 700 GeV and light neutralinos are excluded at 95\% confidence level. In addition, model-independent limits are set on a possible contribution of new phenomena to the signal region yields.},
  language  = {de}
}
@article{OPUS4-17238,
  title     = {Measurements of top-quark pair differential cross-sections in the lepton+jets channel in pp collisions at \( \sqrt{s}=13 \) TeV using the ATLAS detector},
  series = {Journal of High Energy Physics},
  volume    = {2017},
  journal   = {Journal of High Energy Physics},
  number    = {191},
  organization    = {The ATLAS Collaboration},
  doi       = {10.1007/JHEP11(2017)191},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-172386},
  year      = {2017},
  abstract  = {Measurements of differential cross-sections of top-quark pair production in fiducial phase-spaces are presented as a function of top-quark and \(t\overline{t}\) system kinematic observables in proton-proton collisions at a centre-of-mass energy of \(\sqrt{s}\) = 13 TeV. The data set corresponds to an integrated luminosity of 3.2 fb\(^{-1}\), recorded in 2015 with the ATLAS detector at the CERN Large Hadron Collider. Events with exactly one electron or muon and at least two jets in the final state are used for the measurement. Two separate selections are applied that each focus on different top-quark momentum regions, referred to as resolved and boosted topologies of the \(t\overline{t}\) final state. The measured spectra are corrected for detector effects and are compared to several Monte Carlo simulations by means of calculated \(χ^2\) and \(p\)-values.},
  language  = {en}
}
@article{OPUS4-17239,
  title     = {Measurement of the \(t\overline{t}γ\) production cross section in proton-proton collisions at \(\sqrt{s} = 8\) TeV with the ATLAS detector},
  series = {Journal of High Energy Physics},
  volume    = {2017},
  journal   = {Journal of High Energy Physics},
  number    = {86},
  organization    = {The ATLAS Collaboration},
  doi       = {https://doi.org/10.1007/JHEP11(2017)086},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-172399},
  year      = {2017},
  abstract  = {The cross section of a top-quark pair produced in association with a photon is measured in proton-proton collisions at a centre-of-mass energy of \(\sqrt{s} = 8\) TeV with 20.2 fb\(^{-1}\) of data collected by the ATLAS detector at the Large Hadron Collider in 2012. The measurement is performed by selecting events that contain a photon with transverse momentum \(p_T\) > 15 GeV, an isolated lepton with large transverse momentum, large missing transverse momentum, and at least four jets, where at least one is identified as originating from a \(b\)-quark. The production cross section is measured in a fiducial region close to the selection requirements. It is found to be 139 ± 7 (stat.) ± 17 (syst.) fb, in good agreement with the theoretical prediction at next-to-leading order of 151 ± 24 fb. In addition, differential cross sections in the fiducial region are measured as a function of the transverse momentum and pseudorapidity of the photon.},
  language  = {en}
}
@article{OPUS4-17231,
  title     = {Analysis of the Wtb vertex from the measurement of triple-differential angular decay rates of single top quarks produced in the \(t\)-channel at \(\sqrt{s}\) = 8 TeV with the ATLAS detector},
  series = {Journal or High Energy Physics},
  volume    = {2017},
  journal   = {Journal or High Energy Physics},
  number    = {17},
  organization    = {The ATLAS Collaboration},
  doi       = {10.1007/JHEP12(2017)017},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-172310},
  year      = {2017},
  abstract  = {The electroweak production and subsequent decay of single top quarks in the \(t\)-channel is determined by the properties of the \({Wtb}\) vertex, which can be described by the complex parameters of an effective Lagrangian. An analysis of a triple-differential decay rate in \(t\)-channel production is used to simultaneously determine five generalised helicity fractions and phases, as well as the polarisation of the produced top quark. The complex parameters are then constrained. This analysis is based on 20.2 fb\(^{-1}\) of proton-proton collision data at a centre-of-mass energy of 8 TeV collected with the ATLAS detector at the LHC. The fraction of decays containing transversely polarised \(W\) bosons is measured to be \(f_1\) = 0.30 ± 0.05. The phase between amplitudes for transversely and longitudinally polarised \(W\) bosons recoiling against left-handed \(b\)-quarks is measured to be \(\delta\)_ = 0.002\(\pi^{+0.016\pi}_{+0.017\pi}\), giving no indication of CP violation. The fractions of longitudinal or transverse \(W\) bosons accompanied by right-handed \(b\)-quarks are also constrained. Based on these measurements, limits are placed at 95\% CL on the ratio of the complex coupling parameters Re [\({g_R/V_L}\) \(\in\) [-0.12, 0.17] and Im [\({g_R/V_L}\) \(\in\) [-0.07, 0.06]. Constraints are also placed on the ratios |\({V_R}/{V_L}\)| and |\({g_L}/{V_L}\)|. In addition, the polarisation of single top quarks in the \(t\)-channel is constrained to be \(P\) > 0.72 (95\% CL). None of the above measurements make assumptions about the value of any of the other parameters or couplings and all of them are in agreement with the Standard Model.},
  language  = {en}
}
@article{OPUS4-17350,
  title     = {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},
  series = {Journal of High Energy Physics},
  volume    = {2017},
  journal   = {Journal of High Energy Physics},
  number    = {03},
  organization    = {The ATLAS Collaboration},
  doi       = {10.1007/JHEP03(2017)113},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-173505},
  year      = {2017},
  abstract  = {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 different coefficient of the spin density matrix of \(t\overline{t}\) production, which are measured independently. Ten of these observables are measured for the first time. All of them are corrected for detector resolution and acceptance effects back to the parton and stable-particle levels. The measured values of the observables at parton level are compared to Standard Model predictions at next-to-leading order in QCD. The corrected distributions at stable-particle level are presented and the means of the distributions are compared to Monte Carlo predictions. No significant deviation from the Standard Model is observed for any observable.},
  language  = {en}
}
@article{OPUS4-17276,
  title     = {Top-quark mass measurement in the all-hadronic \(t\overline{t}\) decay channel at \(\sqrt{s}=8\) TeV with the ATLAS detector},
  series = {Journal of High Energy Physics},
  volume    = {2017},
  journal   = {Journal of High Energy Physics},
  number    = {09},
  organization    = {The ATLAS Collaboration},
  doi       = {https://doi.org/10.1007/JHEP09(2017)118},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-172762},
  year      = {2017},
  abstract  = {The top-quark mass is measured in the all-hadronic top-antitop quark decay channel using proton-proton collisions at a centre-of-mass energy of \(\sqrt{s}=8\) TeV with the ATLAS detector at the CERN Large Hadron Collider. The data set used in the analysis corresponds to an integrated luminosity of 20.2 fb\(^{-1}\). The large multi-jet background is modelled using a data-driven method. The top-quark mass is obtained from template fits to the ratio of the three-jet to the dijet mass. The three-jet mass is obtained from the three jets assigned to the top quark decay. From these three jets the dijet mass is obtained using the two jets assigned to the W boson decay. The top-quark mass is measured to be 173.72 ± 0.55 (stat.) ± 1.01 (syst.) GeV.},
  language  = {en}
}
@article{OPUS4-17230,
  title     = {Search for new phenomena with large jet multiplicities and missing transverse momentum using large-radius jets and flavour-tagging at ATLAS in 13 TeV \(pp\) collisions},
  series = {Journal of High Energy Physics},
  volume    = {34},
  journal   = {Journal of High Energy Physics},
  organization    = {The ATLAS Collaboration},
  doi       = {10.1007/JHEP12(2017)034},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-172302},
  year      = {2017},
  abstract  = {A search is presented for particles that decay producing a large jet multiplicity and invisible particles. The event selection applies a veto on the presence of isolated electrons or muons and additional requirements on the number of \(b\)-tagged jets and the scalar sum of masses of large-radius jets. Having explored the full ATLAS 2015-2016 dataset of LHC proton-proton collisions at \(\sqrt{s}\) = 13 TeV, which corresponds to 36.1 fb\(^{-1}\) of integrated luminosity, no evidence is found for physics beyond the Standard Model. The results are interpreted in the context of simplified models inspired by R-parity-conserving and R-parity-violating supersymmetry, where gluinos are pair-produced. More generic models within the phenomenological minimal supersymmetric Standard Model are also considered.},
  language  = {en}
}
@article{OPUS4-17232,
  title     = {Search for supersymmetry in events with \(b\)-tagged jets and missing transverse momentum in \(pp\) collisions at \(\sqrt{s}\) = 13 TeV with the ATLAS detector},
  series = {Journal of High Energy Physics},
  volume    = {2017},
  journal   = {Journal of High Energy Physics},
  number    = {195},
  organization    = {The ATLAS Collaboration},
  doi       = {10.1007/JHEP11(2017)195},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-172320},
  year      = {2017},
  abstract  = {A search for the supersymmetric partners of the Standard Model bottom and top quarks is presented. The search uses 36.1 fb\(^{-1}\) of \(pp\) collision data at \(\sqrt{s}\) = 13 TeV collected by the ATLAS experiment at the Large Hadron Collider. Direct production of pairs of bottom and top squarks (\(\overline{b}_1\) and \(\overline{t}_1\)) is searched for in final states with \(b\)-tagged jets and missing transverse momentum. Distinctive selections are defined with either no charged leptons (electrons or muons) in the final state, or one charged lepton. The zero-lepton selection targets models in which the \(\overline{b}_1\) is the lightest squark and decays via \(\overline{b}_1\) → \(b\overline{χ}^0_1\), where \(\overline{χ}^0_1\) is the lightest neutralino. The one-lepton final state targets models where bottom or top squarks are produced and can decay into multiple channels, \(\overline{b}_1\) → \(b\overline{χ}^0_1\) and \(\overline{b}_1\) → \(t\overline{χ}^±_1\), or \(\overline{t}_1\) → \(t\overline{χ}^0_1\) and \(\overline{t}_1\) → \(b\overline{χ}^±_1\), where \(\overline{χ}^±_1\) is the lightest chargino and the mass difference \(m_{\overline{χ}^±_1}\) - \(m_{\overline{χ}^0_1}\) is set to 1 GeV. No excess above the expected Standard Model background is observed. Exclusion limits at 95\% confidence level on the mass of third-generation squarks are derived in various supersymmetry-inspired simplified models.},
  language  = {en}
}
@article{OPUS4-17280,
  title     = {Search for new phenomena in a lepton plus high jet multiplicity final state with the ATLAS experiment using \(\sqrt{s}=13\) TeV proton-proton collision data},
  series = {Journal of High Energy Physics},
  volume    = {2017},
  journal   = {Journal of High Energy Physics},
  number    = {09},
  organization    = {The ATLAS Collaboration},
  doi       = {https://doi.org/10.1007/JHEP09(2017)088},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-172802},
  year      = {2017},
  abstract  = {A search for new phenomena in final states characterized by high jet multiplicity, an isolated lepton (electron or muon) and either zero or at least three \(b\)-tagged jets is presented. The search uses 36.1 fb\(^{-1}\) of \(\sqrt{s}=13\) TeV proton-proton collision data collected by the ATLAS experiment at the Large Hadron Collider in 2015 and 2016. The dominant sources of background are estimated using parameterized extrapolations, based on observables at medium jet multiplicity, to predict the \(b\)-tagged jet multiplicity distribution at the higher jet multiplicities used in the search. No significant excess over the Standard Model expectation is observed and 95\% confidence-level limits are extracted constraining four simplified models of \(R\)-parity-violating supersymmetry that feature either gluino or top-squark pair production. The exclusion limits reach as high as 2.1 TeV in gluino mass and 1.2 TeV in top-squark mass in the models considered. In addition, an upper limit is set on the cross-section for Standard Model \(t\overline{t}t\overline{t}\) production of 60 fb (6.5 × the Standard Model prediction) at 95\% confidence level. Finally, model-independent limits are set on the contribution from new phenomena to the signal-region yields.},
  language  = {en}
}