@article{OPUS4-17323,
  title     = {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},
  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)124},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-173234},
  year      = {2017},
  abstract  = {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 missing transverse momentum and exactly two jets, with one of them identified as likely to contain a \(b\)-hadron. Stringent selection requirements are applied to discriminate \(t\)-channel single-top-quark events from background. The polarisation observables are extracted from asymmetries in angular distributions measured with respect to spin quantisation axes appropriately chosen for the top quark and the \(W\) boson. The asymmetry measurements are performed at parton level by correcting the observed angular distributions for detector effects and hadronisation after subtracting the background contributions. The measured top-quark and \(W\)-boson polarisation values are in agreement with the Standard Model predictions. Limits on the imaginary part of the anomalous coupling \(g_R\) are also set from model independent measurements.},
  language  = {en}
}
@article{OPUS4-17318,
  title     = {Measurement of the \(k_t\) splitting scales in \(Z → ℓℓ\) events in \(pp\) 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    = {08},
  organization    = {The ATLAS Collaboration},
  doi       = {10.1007/JHEP08(2017)026},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-173180},
  year      = {2017},
  abstract  = {A measurement of the splitting scales occuring in the \(k_t\) jet-clustering algorithm is presented for final states containing a \(Z\) boson. The measurement is done using 20.2 fb\(^{-1}\) of proton-proton collision data collected at a centre-of-mass energy of \(\sqrt{s} = 8\) TeV by the ATLAS experiment at the LHC in 2012. The measurement is based on charged-particle track information, which is measured with excellent precision in the \(p_T\) region relevant for the transition between the perturbative and the non-perturbative regimes. The data distributions are corrected for detector effects, and are found to deviate from state-of-the-art predictions in various regions of the observables.},
  language  = {en}
}
@article{OPUS4-17220,
  title     = {Measurement of the Drell-Yan triple-differential cross section in \(pp\) collisions at \(\sqrt{s}\) = 8 TeV},
  series = {Journal of High Energy Physics},
  volume    = {59},
  journal   = {Journal of High Energy Physics},
  organization    = {The ATLAS Collaboration},
  doi       = {10.1007/JHEP12(2017)059},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-172204},
  year      = {2017},
  abstract  = {This paper presents a measurement of the triple-differential cross section for the Drell-Yan process \({Z/γ^*}\) → ℓ\(^+\)ℓ\(^-\) where ℓ is an electron or a muon. The measurement is performed for invariant masses of the lepton pairs, \(m_{ℓℓ}\) , between 46 and 200 GeV using a sample of 20.2 fb\(^{-1}\) of \(pp\) collisions data at a centre-of-mass energy of \(\sqrt{s}\) = 8 TeV collected by the ATLAS detector at the LHC in 2012. The data are presented in bins of invariant mass, absolute dilepton rapidity, |\(y_{ℓℓ}\)|, and the angular variable cos \(θ^*\) between the outgoing lepton and the incoming quark in the Collins-Soper frame. The measurements are performed in the range |\(y_{ℓℓ}\)| < 2.4 in the muon channel, and extended to |\(y_{ℓℓ}\)| < 3.6 in the electron channel. The cross sections are used to determine the \(Z\) boson forward-backward asymmetry as a function of |\(y_{ℓℓ}\)| and \(m_{ℓℓ}\) . The measurements achieve high-precision, below the percent level in the pole region, excluding the uncertainty in the integrated luminosity, and are in agreement with predictions. These precision data are sensitive to the parton distribution functions and the effective weak mixing angle.},
  language  = {en}
}
@article{OPUS4-17217,
  title     = {All-sky search for high-energy neutrinos from gravitational wave event GW170104 with the ANTARES neutrino telescope},
  series = {European Physical Journal C},
  volume    = {77},
  journal   = {European Physical Journal C},
  organization    = {The ANTARES Collaboration},
  doi       = {10.1140/epjc/s10052-017-5451-z},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-172174},
  year      = {2017},
  abstract  = {Advanced LIGO detected a significant gravitational wave signal (GW170104) originating from the coalescence of two black holes during the second observation run on January 4th, 2017. An all-sky high-energy neutrino follow-up search has been made using data from the Antares neutrino telescope, including both upgoing and downgoing events in two separate analyses. No neutrino candidates were found within ±500 s around the GW event time nor any time clustering of events over an extended time window of ±3 months. The non-detection is used to constrain isotropic-equivalent high-energy neutrino emission from GW170104 to less than ∼ 1.2 × \(10^{55}\) erg for a \(E^{-2}\) spectrum. This constraint is valid in the energy range corresponding to the 5-95\% quantiles of the neutrino flux [3.2 TeV; 3.6 PeV], if the GW emitter was below the Antares horizon at the alert time.},
  language  = {en}
}
@article{OPUS4-22546,
  title     = {A search for pair-produced resonances in four-jet final states at root s=13 TeV with the ATLAS detector},
  series = {The European Physical Journal C},
  volume    = {78},
  journal   = {The European Physical Journal C},
  number    = {250},
  organization    = {The ATLAS Collaboration},
  doi       = {10.1140/epjc/s10052-018-5693-4},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-225465},
  pages     = {1-28},
  year      = {2018},
  abstract  = {A search for massive coloured resonances which are pair-produced and decay into two jets is presented. The analysis uses 36.7 fb(-1) of root s = 13 TeV pp collision data recorded by the ATLAS experiment at the LHC in 2015 and 2016. No significant deviation from the background prediction is observed. Results are interpreted in a SUSY simplified model where the lightest supersymmetric particle is the top squark, (t) over tilde, which decays promptly into two quarks through R-parity-violating couplings. Top squarks with masses in the range 100 GeV < m((T) over tilde) < 410 GeV are excluded at 95\% confidence level. If the decay is into a b-quark and a light quark, a dedicated selection requiring two b-tags is used to exclude masses in the ranges 100 GeV < m((t) over tilde) < 470 GeV and 480 GeV < m(<(t)over tilde>) < 610 GeV. Additional limits are set on the pair-production of massive colour-octet resonances.},
  language  = {en}
}
@article{OPUS4-22086,
  title     = {Search for a new heavy gauge-boson resonance decaying into a lepton and missing transverse momentum in 36 fb\(^{-1}\) of \({pp}\) collisions at root s=13 TeV with the ATLAS experiment},
  series = {The European Physical Journal C},
  volume    = {78},
  journal   = {The European Physical Journal C},
  number    = {401},
  organization    = {The ATLAS Collaboration},
  doi       = {10.1140/epjc/s10052-018-5877-y},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-220869},
  pages     = {1-23},
  year      = {2018},
  abstract  = {The results of a search for new heavy W' bosons decaying to an electron or muon and a neutrino using proton-proton collision data at a centre-of-mass energy of root s = 13 TeV are presented. The dataset was collected in 2015 and 2016 by the ATLAS experiment at the Large Hadron Collider and corresponds to an integrated luminosity of 36.1 fb(-1). As no excess of events above the Standard Model prediction is observed, the results are used to set upper limits on the W' boson cross-section times branching ratio to an electron or muon and a neutrino as a function of the W' mass. Assuming a W' boson with the same couplings as the Standard Model W boson, W' masses below 5.1 TeV are excluded at the 95\% confidence level.},
  language  = {en}
}
@article{OPUS4-22670,
  title     = {Search for electroweak production of supersymmetric states in scenarios with compressed mass spectra at root s=13 TeV with the ATLAS detector},
  series = {Physical Review D},
  volume    = {97},
  journal   = {Physical Review D},
  number    = {5},
  organization    = {The ATLAS Collaboration},
  doi       = {10.1103/PhysRevD.97.052010},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226707},
  pages     = {1-35},
  year      = {2018},
  abstract  = {A search for electroweak production of supersymmetric particles in scenarios with compressed mass spectra in final states with two low-momentum leptons and missing transverse momentum is presented. This search uses proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider in 2015-2016, corresponding to 36.1 tb(-1) of integrated luminosity at root s = 13 TeV. Events with same flavor pairs of electrons or muons with opposite electric charge are selected. The data are found to be consistent with the Standard Model prediction. Results are interpreted using simplified models of R-parity conserving supersymmetry in which there is a small mass difference between the masses of the produced supersymmetric particles and the lightest neutralino. Exclusion limits at 95\% confidence level are set on next-to-lightest neutralino masses of up to 145 GeV for Higgsino production and 175 GeV for wino production, and slepton masses of up to 190 GeV for pair production of sleptons. In the compressed mass regime, the exclusion limits extend down to mass splittings of 2.5 GeV for Higgsino production, 2 GeV for wino production, and 1 GeV for slepton production. The results are also interpreted in the context of a radiatively-driven natural supersymmetry model with nonuniversal Higgs boson masses.},
  language  = {en}
}
@article{OPUS4-22082,
  title     = {Measurement of the inclusive and fiducial t(t)over-bar production cross-sections in the lepton+jets channel in \({pp}\) collisions at root s=8 TeV with the ATLAS detector},
  series = {The European Physical Journal C},
  volume    = {78},
  journal   = {The European Physical Journal C},
  number    = {487},
  organization    = {The ATLAS Collaboration},
  doi       = {10.1140/epjc/s10052-018-5904-z},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-220827},
  pages     = {1-31},
  year      = {2018},
  abstract  = {The inclusive and fiducial t (t) over bar production cross sections are measured in the lepton+jets channel using 20.2 fb(-1) of proton proton collision data at a centre-of mass energy of 8 TeV recorded with the ATLAS detector at the LHC. Major systematic uncertainties due to the modelling of the jet energy scale and b-tagging efficiency are constrained by separating selected events into three disjoint regions. In order to reduce systematic uncertainties in the most important background, the W+jets process is modelled using Z+jets events in a data-driven approach. The inclusive t (t) over bar cross-section is measured with a precision of 5.7\% to be (sigma(inc) (t (t) over bar) = 248.3 +/- 0.7 (stat.) +/- 13.4 (syst.) +/- 4.7 (lumi.) pb, assuming a top-quark mass of 172.5 GeV. The result is in agreement with the Standard Model prediction. The cross-section is also measured in a phase space close to that of the selected data. The fiducial cross-section is sigma(fid) (t (t) over bar) = 48.8 +/- 0.1 (stat.) +/- 2.0 (syst.) +/- 0.9 (lumi.) pb with a precision of 4.5\%.},
  language  = {en}
}
@article{OPUS4-22613,
  title     = {Search for pair production of up-type vector-like quarks and for four-top-quark events in final states with multiple \(b\)-jets with the ATLAS detector},
  series = {Journal of High Energy Physics},
  volume    = {89},
  journal   = {Journal of High Energy Physics},
  number    = {7},
  organization    = {The ATLAS Collaboration},
  doi       = {10.1007/JHEP07(2018)089},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226131},
  pages     = {1-67},
  year      = {2018},
  abstract  = {A search for pair production of up-type vector-like quarks (T) with a significant branching ratio into a top quark and either a Standard Model Higgs boson or a Z boson is presented. The same analysis is also used to search for four-top-quark production in several new physics scenarios. The search is based on a dataset of pp collisions at root s = 13TeV recorded in 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider and corresponds to an integrated luminosity of 36.1 fb(-1). Data are analysed in the lepton+jets final state, characterised by an isolated electron or muon with high transverse momentum, large missing transverse momentum and multiple jets, as well as the jets+E-T(miss) final state, characterised by multiple jets and large missing transverse momentum. The search exploits the high multiplicity of jets identified as originating from b-quarks, and the presence of boosted, hadronically decaying top quarks and Higgs bosons reconstructed as large-radius jets, characteristic of signal events. No significant excess above the Standard Model expectation is observed, and 95\% CL upper limits are set on the production cross sections for the different signal processes considered. These cross-section limits are used to derive lower limits on the mass of a vector-like T quark under several branching ratio hypotheses assuming contributions from T -> Wb, Zt, Ht decays. The 95\% CL observed lower limits on the T quark mass range between 0.99TeV and 1.43TeV for all possible values of the branching ratios into the three decay modes considered, significantly extending the reach beyond that of previous searches. Additionally, upper limits on anomalous four-top-quark production are set in the context of an effective field theory model, as well as in an universal extra dimensions model.},
  language  = {en}
}
@article{OPUS4-31736,
  title     = {Search for heavy particles decaying into a top-quark pair in the fully hadronic final state in \({pp}\) collisions at root s=13 TeV with the ATLAS detector},
  series = {Physical Review D},
  volume    = {99},
  journal   = {Physical Review D},
  number    = {9},
  organization    = {The ATLAS Collaboration},
  doi       = {10.1103/PhysRevD.99.092004},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-317362},
  pages     = {1-38},
  year      = {2019},
  abstract  = {A search for new particles decaying into a pair of top quarks is performed using proton-proton collision data recorded with the ATLAS detector at the Large Hadron Collider at a center-of-mass energy of root s = 13 TeV corresponding to an integrated luminosity of 36.1 fb(-1). Events consistent with top-quark pair production and the fully hadronic decay mode of the top quarks are selected by requiring multiple high transverse momentum jets including those containing b-hadrons. Two analysis techniques, exploiting dedicated top-quark pair reconstruction in different kinematic regimes, are used to optimize the search sensitivity to new hypothetical particles over a wide mass range. The invariant mass distribution of the two reconstructed top-quark candidates is examined for resonant production of new particles with various spins and decay widths. No significant deviation from the Standard Model prediction is observed and limits are set on the production cross-section times branching fraction for new hypothetical Z' bosons, dark-matter mediators, Kaluza-Klein gravitons and Kaluza-Klein gluons. By comparing with the predicted production cross sections, the Z' boson in the topcolor-assisted-technicolor model is excluded for masses up to 3.1-3.6 TeV, the dark-matter mediators in a simplified framework are excluded in the mass ranges from 0.8 to 0.9 TeV and from 2.0 to 2.2 TeV, and the Kaluza-Klein gluon is excluded for masses up to 3.4 TeV, depending on the decay widths of the particles.},
  language  = {en}
}