@article{OPUS4-22656,
  title     = {Evidence for the associated production of the Higgs boson and a top quark pair with the ATLAS detector},
  series = {Physical Review D},
  volume    = {97},
  journal   = {Physical Review D},
  organization    = {The ATLAS Collaboration},
  doi       = {10.1103/PhysRevD.97.072003},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226569},
  pages     = {1-44},
  year      = {2018},
  abstract  = {A search for the associated production of the Higgs boson with a top quark pair (tt (b) over barH) is reported. The search is performed in multilepton final states using a data set corresponding to an integrated luminosity of 36.1 fb(-1) of proton-proton collision data recorded by the ATLAS experiment at a center-of-mass energy root s = 13 TeV at the Large Hadron Collider. Higgs boson decays to WW*, tau tau, and ZZ* are targeted. Seven final states, categorized by the number and flavor of charged-lepton candidates, are examined for the presence of the Standard Model Higgs boson with a mass of 125 GeVand a pair of top quarks. An excess of events over the expected background from Standard Model processes is found with an observed significance of 4.1 standard deviations, compared to an expectation of 2.8 standard deviations. The best fit for the (tt (b) over barH) production cross section is sot (tt (b) over barH) = 790(-210)(+230) fb, in agreement with the Standard Model prediction of 507(-50)(+35) fb. The combination of this result with other tt (b) over barH searches from the ATLAS experiment using the Higgs boson decay modes to b (b) over bar, gamma gamma and ZZ* -> 4l, has an observed significance of 4.2 standard deviations, compared to an expectation of 3.8 standard deviations. This provides evidence for the tt (b) over barH production mode.},
  language  = {en}
}
@article{OPUS4-22677,
  title     = {Measurements of t(t)over-bar differential cross-sections of highly boosted top quarks decaying to all-hadronic final states in \(pp\) collisions at root \(s\)=13 Te V using the ATLAS detector},
  series = {Physical Review D},
  volume    = {98},
  journal   = {Physical Review D},
  organization    = {The ATLAS Collaboration},
  doi       = {10.1103/PhysRevD.98.012003},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226771},
  pages     = {39},
  year      = {2018},
  abstract  = {Measurements are made of differential cross-sections of highly boosted pair-produced top quarks as a function of top-quark and t (t) over bar system kinematic observables using proton-proton collisions at a center-of-mass energy of root s = 13 TeV. The data set corresponds to an integrated luminosity of 36.1 fb(-1), recorded in 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider. Events with two large-radius jets in the final state, one with transverse momentum p(T) > 500 GeV and a second with p(T) > 350 GeV, are used for the measurement. The top-quark candidates are separated from the multijet background using jet substructure information and association with a b-tagged jet. The measured spectra are corrected for detector effects to a particle-level fiducial phase space and a parton-level limited phase space, and are compared to several Monte Carlo simulations by means of calculated chi(2) values. The cross-section for t (t) over bar production in the fiducial phase-space region is 292 +/- 7(stat) +/- 71(syst) tb, to be compared to the theoretical prediction of 384 +/- 36 fb.},
  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}
}
@article{OPUS4-22654,
  title     = {Search for the standard model Higgs boson produced in association with top quarks and decaying into a b(b)overbar pair in \(pp\) collisions at root \(s\)=13 TeV with the ATLAS detector},
  series = {Physical Review D},
  volume    = {97},
  journal   = {Physical Review D},
  number    = {7},
  organization    = {The ATLAS Collaboration},
  doi       = {10.1103/PhysRevD.97.072016},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226545},
  pages     = {1-44},
  year      = {2018},
  abstract  = {A search for the standard model Higgs boson produced in association with a top-quark pair, t(t)overbarH, is presented. The analysis uses 36.1 fb(-1) of pp collision data at root s = 13 TeV collected with the ATLAS detector at the Large Hadron Collider in 2015 and 2016. The search targets the H -> b(b)overbar decay mode. The selected events contain either one or two electrons or muons from the top-quark decays, and are then categorized according to the number of jets and how likely these are to contain b-hadrons. Multivariate techniques are used to discriminate between signal and background events, the latter being dominated by ft + jets production. For a Higgs boson mass of 125 GeV, the ratio of the measured t(t)overbarH signal cross-section to the standard model expectation is found to be mu = 0.84(-0.61)(+0.64). A value of mu greater than 2.0 is excluded at 95\% confidence level (C.L.) while the expected upper limit is mu < 1.2 in the absence of a t(t)overbarH signal.},
  language  = {en}
}
@article{OPUS4-22608,
  title     = {Search for top squarks decaying to tau sleptons in \(pp\) collisions at root \(s\)=13 TeV with the ATLAS detector},
  series = {Physical Review D},
  volume    = {98},
  journal   = {Physical Review D},
  organization    = {The ATLAS Collaboration},
  doi       = {10.1103/PhysRevD.98.032008},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226080},
  pages     = {1-33},
  year      = {2018},
  abstract  = {A search for direct pair production of top squarks in final states with two tau leptons, b-jets, and missing transverse momentum is presented. The analysis is based on proton-proton collision data at root s = 13 TeV corresponding to an integrated luminosity of 36.1 fb(-1) recorded with the ATLAS detector at the Large Hadron Collider in 2015 and 2016. Two exclusive channels with either two hadronically decaying tau leptons or one hadronically and one leptonically decaying tau lepton are considered. No significant deviation from the Standard Model predictions is observed in the data. The analysis results are interpreted in terms of model-independent limits and used to derive exclusion limits on the masses of the top squark (t) over tilde (1) and the tau slepton (tau) over tilde (1) in a simplified model of supersymmetry with a nearly massless gravitino. In this model, masses up to m((t) over tilde (1)) = 1.16 TeV and m ((tau) over tilde (1)) = 1.00 TeV are excluded at 95\% confidence level.},
  language  = {en}
}