@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{OPUS4-22600, title = {Search for pair production of Higgs bosons in the \({bb̅bb̅}\) final state using proton-proton collisions at root s=13 TeV with the ATLAS detector}, series = {Journal of High Energy Physics}, volume = {30}, journal = {Journal of High Energy Physics}, organization = {The ATLAS Collaboration}, doi = {10.1007/JHEP01(2019)030}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226001}, pages = {1-48}, year = {2018}, abstract = {A search for Higgs boson pair production in the bbbb final state is carried out with up to 36.1 fb(-1) of LHC proton-proton collision data collected at s=13 TeV with the ATLAS detector in 2015 and 2016. Three benchmark signals are studied: a spin-2 graviton decaying into a Higgs boson pair, a scalar resonance decaying into a Higgs boson pair, and Standard Model non-resonant Higgs boson pair production. Two analyses are carried out, each implementing a particular technique for the event reconstruction that targets Higgs bosons reconstructed as pairs of jets or single boosted jets. The resonance mass range covered is 260-3000 GeV. The analyses are statistically combined and upper limits on the production cross section of Higgs boson pairs times branching ratio to bbbb are set in each model. No significant excess is observed; the largest deviation of data over prediction is found at a mass of 280 GeV, corresponding to 2.3 standard deviations globally. The observed 95\% confidence level upper limit on the non-resonant production is 13 times the Standard Model prediction.}, language = {en} } @article{OPUS4-22069, title = {Measurement of the Soft-Drop Jet Mass in \({pp}\) Collisions at root s=13 TeV with the ATLAS Detector}, series = {Physical Review Letters}, volume = {121}, journal = {Physical Review Letters}, number = {9}, organization = {The ATLAS Collaboration}, doi = {10.1103/PhysRevLett.121.092001}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-220694}, pages = {1-20}, year = {2018}, abstract = {Jet substructure observables have significantly extended the search program for physics beyond the standard model at the Large Hadron Collider. The state-of-the-art tools have been motivated by theoretical calculations, but there has never been a direct comparison between data and calculations of jet substructure observables that are accurate beyond leading-logarithm approximation. Such observables are significant not only for probing the collinear regime of QCD that is largely unexplored at a hadron collider, but also for improving the understanding of jet substructure properties that are used in many studies at the Large Hadron Collider. This Letter documents a measurement of the first jet substructure quantity at a hadron collider to be calculated at next-to-next-to-leading-logarithm accuracy. The normalized, differential cross section is measured as a function of log(10)rho(2), where rho is the ratio of the soft-drop mass to the ungroomed jet transverse momentum. This quantity is measured in dijet events from 32.9 fb(-1) of root s = 13 TeV proton-proton collisions recorded by the ATLAS detector. The data are unfolded to correct for detector effects and compared to precise QCD calculations and leading-logarithm particle-level Monte Carlo simulations.}, language = {en} } @article{OPUS4-22593, title = {Search for dark matter produced in association with bottom or top quarks in root s=13 TeV \({pp}\) collisions with the ATLAS detector}, series = {European Physical Journal C}, volume = {C 78}, journal = {European Physical Journal C}, number = {18}, organization = {The ATLAS Collaboration}, doi = {10.1140/epjc/s10052-017-5486-1}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-225937}, pages = {1-36}, year = {2018}, abstract = {A search for weakly interacting massive dark matter particles produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and missing transverse momentum are considered. The analysis uses 36.1 fb(-1) of proton proton collision data recorded by the ATLAS experiment at root s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are interpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour-neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross-section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour-charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements.}, language = {en} } @article{OPUS4-22602, title = {Measurements of differential cross sections of top quark pair production in association with jets in pp collisions at root s=13 TeV using the ATLAS detector}, series = {Journal of High Energy Physics}, volume = {159}, journal = {Journal of High Energy Physics}, number = {10}, organization = {The ATLAS Collaboration}, doi = {10.1007/JHEP10(2018)159}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226023}, pages = {1-57}, year = {2018}, abstract = {Measurements of di ff erential cross sections of top quark pair production in association with jets by the ATLAS experiment at the LHC are presented. The measurements are performed as functions of the top quark transverse momentum, the transverse momentum of the top quark-antitop quark system and the out-of-plane transverse momentum using data from pp collisions at p s = 13TeV collected by the ATLAS detector at the LHC in 2015 and corresponding to an integrated luminosity of 3.2 fb. The top quark pair events are selected in the lepton (electron or muon) + jets channel. The measured cross sections, which are compared to several predictions, allow a detailed study of top quark production.}, language = {en} } @article{OPUS4-22611, title = {Search for flavour-changing neutral current top-quark decays \(t\) -> \({qZ}\) in proton-proton collisions at root s=13 TeV with the ATLAS detector}, series = {Journal of High Energy Physics}, volume = {176}, journal = {Journal of High Energy Physics}, number = {7}, organization = {The ATLAS Collaboration}, doi = {10.1007/JHEP07(2018)176}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226114}, pages = {1-40}, year = {2018}, abstract = {A search for flavour-changing neutral-current processes in top-quark decays is presented. Data collected with the ATLAS detector from proton-proton collisions at the Large Hadron Collider at a centre-of-mass energy of root s = 13TeV, corresponding to an integrated luminosity of 36.1 fb(-1), are analysed. The search is performed using top-quark pair events, with one top quark decaying through the t -> qZ (q = u, c) flavour-changing neutral-current channel, and the other through the dominant Standard Model mode t -> bW. Only Z boson decays into charged leptons and leptonic W boson decays are considered as signal. Consequently, the final-state topology is characterized by the presence of three isolated charged leptons (electrons or muons), at least two jets, one of the jets originating from a b-quark, and missing transverse momentum from the undetected neutrino. The data are consistent with Standard Model background contributions, and at 95\% confidence level the search sets observed (expected) upper limits of 1.7 x 10(-4) (2.4 x 10(-4)) on the t -> uZ branching ratio and 2.4 x 10(-4) (3.2 x 10(-4)) on the t -> cZ branching ratio, constituting the most stringent limits to date.}, language = {en} } @article{OPUS4-22615, title = {Measurement of the production cross section of three isolated photons in \({pp}\) collisions at root \(s\)=8 TeV using the ATLAS detector}, series = {Physics Letters B}, volume = {781}, journal = {Physics Letters B}, organization = {The ATLAS Collaboration}, doi = {10.1016/j.physletb.2018.03.057}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226154}, pages = {55-76}, year = {2018}, abstract = {A measurement of the production of three isolated photons in proton-proton collisions at a centre-of-mass energy root s = 8 TeV is reported. The results are based on an integrated luminosity of 20.2 fb(-1) collected with the ATLAS detector at the LHC. The differential cross sections are measured as functions of the transverse energy of each photon, the difference in azimuthal angle and in pseudorapidity between pairs of photons, the invariant mass of pairs of photons, and the invariant mass of the triphoton system. A measurement of the inclusive fiducial cross section is also reported. Next-to-leading-order perturbative QCD predictions are compared to the cross-section measurements. The predictions underestimate the measurement of the inclusive fiducial cross section and the differential measurements at low photon transverse energies and invariant masses. They provide adequate descriptions of the measurements at high values of the photon transverse energies, invariant mass of pairs of photons, and invariant mass of the triphoton system. (C) 2018 The Author. Published by Elsevier B.V.}, language = {en} } @article{OPUS4-17354, title = {Measurements of top-quark pair to \(Z\)-boson cross-section ratios at \(\sqrt{s}\) \(=13 , 8, 7\) TeV with the ATLAS detector}, series = {Journal of High Energy Physics}, volume = {2017}, journal = {Journal of High Energy Physics}, number = {02}, organization = {The ATLAS Collaboration}, doi = {10.1007/JHEP02(2017)117}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-173544}, year = {2017}, abstract = {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 \(\sqrt{s}\), are evaluated. The ratios are constructed using previously published ATLAS measurements of the \({t\overline{t}}\) and \(Z\)-boson production cross sections, corrected to a common phase space where required, and a new analysis of \(Z\) → ℓ\(^+\)ℓ\(^-\) where ℓ = \(e, µ\) at \(\sqrt{s}\) = 13 TeV performed with data collected in 2015 with an integrated luminosity of 3.2 fb\(^-1\). Correlations of systematic uncertainties are taken into account when evaluating the uncertainties in the ratios. The correlation model is also used to evaluate the combined cross section of the \(Z\) → \(e\)\(^+\)\(e\)\(^-\) and the \(Z\) → \(µ\)\(^+\)\(µ\)\(^-\) channels for each \(\sqrt{s}\) value. The results are compared to calculations performed at next-to-next-to-leading-order accuracy using recent sets of parton distribution functions. The data demonstrate significant power to constrain the gluon distribution function for the Bjorken-\(x\) values near 0.1 and the light-quark sea for \(x\) < 0.02.}, language = {en} } @article{OPUS4-17361, title = {Measurement of the \(ZZ\) production cross section in proton-proton collisions at \(\sqrt{s}\) = 8 TeV using the \(ZZ\) → \(ℓ^-ℓ^+ℓ^{′-}ℓ^{′+}\) and \(ZZ\) → \(ℓ^-ℓ^+{ν\overline{ν}}\) decay channels with the ATLAS detector}, series = {Journal of High Energy Physics}, volume = {2017}, journal = {Journal of High Energy Physics}, number = {99}, organization = {The ATLAS Collaboration}, doi = {10.1007/JHEP01(2017)099}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-173616}, year = {2017}, abstract = {A measurement of the \(ZZ\) production cross section in the \(ℓ^-ℓ^+ℓ^{′-}ℓ^{′+}\) and \(ℓ^-ℓ^+{ν\overline{ν}}\) channels (ℓ = e, µ) in proton-proton collisions at \(\sqrt{s}\) = 8TeV 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 \(ZZ\) → \(ℓ^-ℓ^+ℓ^{′-}ℓ^{′+}\) and \(ZZ\) → \(ℓ^-ℓ^+{ν\overline{ν}}\) are measured in selected phase-space regions. The total cross section for \(ZZ\) events produced with both \(Z\) bosons in the mass range 66 to 116GeV is measured from the combination of the two channels to be 7.3 ± 0.4(stat) ± 0.3 (syst)\(^{-0.2}_{-0.1}\) (lumi) pb, which is consistent with the Standard Model prediction of 6.6\(^{+0.7}_{-0.6}\) pb. The differential cross sections in bins of various kinematic variables are presented. The differential event yield as a function of the transverse momentum of the leading \(Z\) boson is used to set limits on anomalous neutral triple gauge boson couplings in \(ZZ\) production.}, language = {en} } @article{OPUS4-17366, title = {Measurement of the \({t\overline{t}}Z\) and \({t\overline{t}}W\) production cross sections in multilepton final states using 3.2 fb\(^{-1}\) of \(pp\) collisions at \(\sqrt{s}\) = 13 TeV with the ATLAS detector}, series = {European Physical Journal C}, volume = {77}, journal = {European Physical Journal C}, number = {40}, organization = {The ATLAS Collaboration}, doi = {10.1140/epjc/s10052-016-4574-y}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-173662}, year = {2017}, abstract = {A measurement of the \({t\overline{t}}Z\) and \({t\overline{t}}W\) 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 luminosity of 3.2 fb\(^{-1}\). The inclusive cross sections are extracted using likelihood fits to signal and control regions, resulting in \(\sigma_{{t\overline{t}}Z}\) = 0.9 ± 0.3 pb and \(\sigma_{{t\overline{t}}W}\) = 1.5 ± 0.8 pb, in agreement with the Standard Model predictions.}, language = {en} } @article{OPUS4-14305, title = {Search for a CP-odd Higgs boson decaying to Zh in pp collisions at \(\sqrt{s}\)=8 TeV with the ATLAS detector}, series = {Physics Letters B}, volume = {744}, journal = {Physics Letters B}, organization = {ATLAS Collaboration}, doi = {10.1016/j.physletb.2015.03.054}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-143050}, pages = {163-183}, year = {2015}, abstract = {A search for a heavy, CP-odd Higgs boson, A, decaying into a Z boson and a 125 GeV Higgs boson, h, with the ATLAS detector at the LHC is presented. The search uses proton-proton collision data at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 20.3 fb\(^{-1}\). Decays of CP-even h bosons to ττ or bb pairs with the Z boson decaying to electron or muon pairs are considered, as well as h→bb decays with the Z boson decaying to neutrinos. No evidence for the production of an A boson in these channels is found and the 95\% confidence level upper limits derived for σ(gg→A)×BR(A→Zh)×BR(h→f\(\bar{f}\)) are 0.098-0.013 pb for f=τ and 0.57-0.014 pb for f=b in a range of m\(_{A}\)=220-1000 GeVmA=220-1000 GeV. The results are combined and interpreted in the context of two-Higgs-doublet models.}, language = {en} } @article{OPUS4-19073, title = {Long-term outcome of patients with newly diagnosed chronic myeloid leukemia: a randomized comparison of stem cell transplantation with drug treatment}, series = {Leukemia}, volume = {30}, journal = {Leukemia}, number = {3}, organization = {SAKK}, doi = {10.1038/leu.2015.281}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-190738}, pages = {562 -- 569}, year = {2016}, abstract = {Tyrosine kinase inhibitors represent today's treatment of choice in chronic myeloid leukemia (CML). Allogeneic hematopoietic stem cell transplantation (HSCT) is regarded as salvage therapy. This prospective randomized CML-study IIIA recruited 669 patients with newly diagnosed CML between July 1997 and January 2004 from 143 centers. Of these, 427 patients were considered eligible for HSCT and were randomized by availability of a matched family donor between primary HSCT (group A; N = 166 patients) and best available drug treatment (group B; N = 261). Primary end point was long-term survival. Survival probabilities were not different between groups A and B (10-year survival: 0.76 (95\% confidence interval (CI): 0.69-0.82) vs 0.69 (95\% CI: 0.61-0.76)), but influenced by disease and transplant risk. Patients with a low transplant risk showed superior survival compared with patients with high( P < 0.001) and non-high-risk disease (P = 0.047) in group B; after entering blast crisis, survival was not different with or without HSCT. Significantly more patients in group A were in molecular remission (56\% vs 39\%; P = 0.005) and free of drug treatment (56\% vs 6\%; P < 0.001). Differences in symptoms and Karnofsky score were not significant. In the era of tyrosine kinase inhibitors, HSCT remains a valid option when both disease and transplant risk are considered.}, language = {en} } @article{OPUS4-17322, title = {Studies of \(Zγ\) production in association with a high-mass dijet system 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 = {07}, organization = {The ATLAS Collaboration}, doi = {https://doi.org/10.1007/JHEP07(2017)107}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-173229}, year = {2017}, abstract = {The production of a \(Z\) boson and a photon in association with a high-mass dijet system is studied using 20.2 fb\(^{-1}\) of proton-proton collision data at a centre-of-mass energy of \(\sqrt{s}\) = 8 TeV recorded with the ATLAS detector in 2012 at the Large Hadron Collider. Final states with a photon and a Z boson decaying into a pair of either electrons, muons, or neutrinos are analysed. Electroweak and total \(pp\) → \(Zγjj\) cross-sections are extracted in two fiducial regions with different sensitivities to electroweak production processes. Quartic couplings of vector bosons are studied in regions of phase space with an enhanced contribution from pure electroweak production, sensitive to vector-boson scattering processes \(V V → Zγ\). No deviations from Standard Model predictions are observed and constraints are placed on anomalous couplings parameterized by higher-dimensional operators using effective field theory.}, language = {en} } @article{OPUS4-17247, title = {Search for pair production of heavy vector-like quarks decaying to high-\(p_T\) \(W\) bosons and \(b\) quarks in the lepton-plus-jets final state 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 = {141}, organization = {The ATLAS Collaboration}, doi = {10.1007/JHEP10(2017)141}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-172472}, year = {2017}, abstract = {A search is presented for the pair production of heavy vector-like \(T\) quarks, primarily targeting the \(T\) quark decays to a \(W\) boson and a \(b\)-quark. The search is based on 36.1 fb\(^{-1}\) of \(pp\) collisions at \(\sqrt{s}=13\) TeV recorded in 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider. Data are analysed in the lepton-plus-jets final state, including at least one \(b\)-tagged jet and a large-radius jet identified as originating from the hadronic decay of a high-momentum \(W\) boson. No significant deviation from the Standard Model expectation is observed in the reconstructed \(T\) mass distribution. The observed 95\% confidence level lower limit on the \(T\) mass are 1350 GeV assuming 100\% branching ratio to \(Wb\). In the SU(2) singlet scenario, the lower mass limit is 1170 GeV. This search is also sensitive to a heavy vector-like \(B\) quark decaying to \(Wt\) and other final states. The results are thus reinterpreted to provide a 95\% confidence level lower limit on the \(B\) quark mass at 1250 GeV assuming 100\% branching ratio to \(Wt\); in the SU(2) singlet scenario, the limit is 1080 GeV. Mass limits on both \(T\) and \(B\) production are also set as a function of the decay branching ratios. The 100\% branching ratio limits are found to be applicable to heavy vector-like \(Y\) and \(X\) production that decay to \(Wb\) and \(Wt\), respectively.}, 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{OPUS4-17246, title = {Search for new high-mass phenomena in the dilepton final state using 36 fb\(^{-1}\) of proton-proton collision data at \(\sqrt{s}=13\) TeV with the ATLAS detector}, series = {Journal of High Energy Physics}, volume = {2017}, journal = {Journal of High Energy Physics}, number = {182}, organization = {The ATLAS Collaboration}, doi = {10.1007/JHEP10(2017)182}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-172462}, year = {2017}, abstract = {A search is conducted for new resonant and non-resonant high-mass phenomena in dielectron and dimuon final states. The search uses 36.1 fb\(^{-1}\) of proton-proton collision data, collected at \(\sqrt{s}=13\) TeV by the ATLAS experiment at the LHC in 2015 and 2016. No significant deviation from the Standard Model prediction is observed. Upper limits at 95\% credibility level are set on the cross-section times branching ratio for resonances decaying into dileptons, which are converted to lower limits on the resonance mass, up to 4.1 TeV for the E\(_6\)-motivated \(Z^′_χ\). Lower limits on the \({qqℓℓ}\) contact interaction scale are set between 2.4 TeV and 40 TeV, depending on the model.}, language = {en} } @article{OPUS4-17312, title = {Measurement of the inclusive jet cross-sections 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 = {09}, organization = {The ATLAS Collaboration}, doi = {10.1007/JHEP09(2017)020}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-173123}, year = {2017}, abstract = {Inclusive jet production cross-sections are measured in proton-proton collisions at a centre-of-mass energy of \(\sqrt{s} = 8\) TeV recorded by the ATLAS experiment at the Large Hadron Collider at CERN. The total integrated luminosity of the analysed data set amounts to 20.2 fb\(^{-1}\). Double-differential cross-sections are measured for jets defined by the anti-\(k_t\) jet clustering algorithm with radius parameters of \(R\) = 0.4 and \(R\) = 0.6 and are presented as a function of the jet transverse momentum, in the range between 70 GeV and 2.5 TeV and in six bins of the absolute jet rapidity, between 0 and 3.0. The measured cross-sections are compared to predictions of quantum chromodynamics, calculated at next-to-leading order in perturbation theory, and corrected for non-perturbative and electroweak effects. The level of agreement with predictions, using a selection of different parton distribution functions for the proton, is quantified. Tensions between the data and the theory predictions are observed.}, language = {en} } @article{OPUS4-17321, title = {Search for direct top squark pair production in events with a Higgs or \(Z\) boson, and missing transverse momentum in \(\sqrt{s}\) = 13 TeV \(pp\) collisions 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 = {https://doi.org/10.1007/JHEP08(2017)006}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-173210}, year = {2017}, abstract = {A search for direct top squark pair production resulting in events with either a same-flavour opposite-sign dilepton pair with invariant mass compatible with a \(Z\) boson or a pair of jets compatible with a Standard Model (SM) Higgs boson (\(h\)) is presented. Requirements on the missing transverse momentum, together with additional selections on leptons, jets, jets identified as originating from \(b\)-quarks are imposed to target the other decay products of the top squark pair. The analysis is performed using proton-proton collision data at \(\sqrt{s}\) = 13 TeV collected with the ATLAS detector at the LHC in 2015-2016, corresponding to an integrated luminosity of 36.1 fb\(^{-1}\). No excess is observed in the data with respect to the SM predictions. The results are interpreted in two sets of models. In the first set, direct production of pairs of lighter top squarks (\(\tilde{t}_1\)) with long decay chains involving \(Z\) or Higgs bosons is considered. The second set includes direct pair production of the heavier top squark pairs (\(\tilde{t}_2\)) decaying via \(\tilde{t}_2\) → \(Z\tilde{t}_1\) or \(\tilde{t}_2\) → \(h\tilde{t}_1\). The results exclude at 95\% confidence level \(\tilde{t}_2\) and \(\tilde{t}_1\) masses up to about 800 GeV, extending the exclusion region of supersymmetric parameter space covered by previous LHC searches.}, language = {en} } @article{OPUS4-31266, title = {Combination of inclusive and differential t(t)over-bar charge asymmetry measurements using ATLAS and CMS data at root S=7 and 8 TeV}, series = {Journal of High Energy Physics}, volume = {33}, journal = {Journal of High Energy Physics}, number = {4}, organization = {The ATLAS collaboration and the CMS collaboration}, doi = {10.1007/JHEP04(2018)033}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-312669}, pages = {1-67}, year = {2018}, abstract = {This paper presents combinations of inclusive and differential measurements of the charge asymmetry (A(C)) in top quark pair (t(t)over-bar) events with a lepton+jets signature by the ATLAS and CMS Collaborations, using data from LHC proton-proton collisions at centre-of-mass energies of 7 and 8 TeV. The data correspond to integrated luminosities of about 5 and 20 fb(-1) for each experiment, respectively. The resulting combined LHC measurements of the inclusive charge asymmetry are A(C)(LHC7) = 0.005 +/- 0.007 (stat) +/- 0.006 (syst) at 7 TeV and A(C)(LHC8) = 0.0055 +/- 0.0023 (stat) +/- 0.0025 (syst) at 8 TeV. These values, as well as the combination of A(C) measurements as a function of the invariant mass of the t(t)over-bar system at 8 TeV, are consistent with the respective standard model predictions.}, language = {en} } @article{OPUS4-31268, title = {Search for new phenomena in events with same-charge leptons and b-jets in pp collisions at √\(s\) = 13 TeV with the ATLAS detector}, series = {Journal of High Energy Physics}, volume = {12}, journal = {Journal of High Energy Physics}, number = {39}, organization = {The ATLAS Collaboration}, doi = {10.1007/JHEP12(2018)039}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-312681}, pages = {1-55}, year = {2018}, abstract = {A search for new phenomena in events with two same- charge leptons or three leptons and jets identi fi ed as originating from b - quarks in a data sample of 36.1 fb of pp collisions at ps = 13TeV recorded by the ATLAS detector at the Large Hadron Collider is reported. No signi fi cant excess is found and limits are set on vector- like quark, fourtop- quark, and same- sign top- quark pair production. The observed ( expected) 95\% CL mass limits for a vector- like T - and B - quark singlet are mT > 0 : 98 ( 0 : 99) TeV and mB > 1 : 00 ( 1 : 01) TeV respectively. Limits on the production of the vector- like T5=3 - quark are also derived considering both pair and single production; in the former case the lower limit on the mass of the T5=3 - quark is ( expected to be) 1.19 ( 1.21) TeV. The Standard Model fourtop- quark production cross- section upper limit is ( expected to be) 69 ( 29) fb. Constraints are also set on exotic four- top- quark production models. Finally, limits are set on samesign top- quark pair production. The upper limit on uu ! tt production is ( expected to be) 89 ( 59) fb for a mediator mass of 1TeV, and a dark- matter interpretation is also derived, excluding a mediator of 3TeV with a dark- sector coupling of 1.0 and a coupling to ordinary matter above 0.31.}, language = {en} }