@article{OPUS4-12799, title = {Measurements of the pseudorapidity dependence of the total transverse energy in proton-proton collisions at √s=7 TeV with ATLAS}, series = {Journal of High Energy Physics}, volume = {11}, journal = {Journal of High Energy Physics}, number = {033}, organization = {ATLAS Collaboration}, doi = {10.1007/JHEP11(2012)033}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-127998}, year = {2012}, abstract = {This paper describes measurements of the sum of the transverse energy of particles as a function of particle pseudorapidity, η, in proton-proton collisions at a centre-of-mass energy, √s=7 TeV using the ATLAS detector at the Large Hadron Collider. The measurements are performed in the region |η| < 4.8 for two event classes: those requiring the presence of particles with a low transverse momentum and those requiring particles with a significant transverse momentum. In the second dataset measurements are made in the region transverse to the hard scatter. The distributions are compared to the predictions of various Monte Carlo event generators, which generally tend to underestimate the amount of transverse energy at high |η|.}, language = {en} } @article{OPUS4-12761, title = {Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at √s=7 TeV with the ATLAS experiment}, series = {The European Physical Journal C}, volume = {72}, journal = {The European Physical Journal C}, number = {2001}, organization = {ATLAS Collaboration}, doi = {10.1140/epjc/s10052-012-2001-6}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-127615}, year = {2012}, abstract = {This paper describes an analysis of the angular distribution of W→eν and W→μν decays, using data from pp collisions at s√=7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb\(^{-1}\). Using the decay lepton transverse momentum and the missing transverse momentum, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f\(_0\), f\(_L\) and f\(_R\) over two ranges of W transverse momentum (p\(^W_T\)):3550 GeV. Good agreement is found with theoretical predictions. For p\(^W_T\)>50 GeV, the values of f\(_0\) and f\(_L\)-f\(_R\), averaged over charge and lepton flavour, are measured to be: f\(_0\)=0.127±0.030±0.108 and f\(_L\)-f\(_R\)=0.252±0.017±0.030, where the first uncertainties are statistical, and the second include all systematic effects.}, language = {en} } @article{OPUS4-12762, title = {Rapidity gap cross sections measured with the ATLAS detector in pp collisions at √s=7TeV}, series = {The European Physical Journal C}, volume = {72}, journal = {The European Physical Journal C}, number = {1926}, organization = {ATLAS Collaboration}, doi = {10.1140/epjc/s10052-012-1926-0}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-127629}, year = {2012}, abstract = {Pseudorapidity gap distributions in proton-proton collisions at √s=7 TeV are studied using a minimum bias data sample with an integrated luminosity of 7.1 μb\(^{-1}\). Cross sections are measured differentially in terms of Δη\(^F\), the larger of the pseudorapidity regions extending to the limits of the ATLAS sensitivity, at η=±4.9, in which no final state particles are produced above a transverse momentum threshold pcutT. The measurements span the region 0<Δη\(^F\)<8 for 200MeV ZX/XX -> 4l , where X is a new vector boson Z(d) or pseudoscalar a with mass between 1 and 60 GeV. The search uses pp collision data collected with the ATLAS detector at the LHC with an integrated luminosity of 36.1 fb(-1) at a centre-of-mass energy root s = 13TeV. No significant excess of events above Standard Model background predictions is observed; therefore, upper limits at 95\% confidence level are set on model-independent fiducial cross-sections, and on the Higgs boson decay branching ratios to vector and pseudoscalar bosons in two benchmark models.}, language = {en} } @article{OPUS4-12915, title = {A search for flavour changing neutral currents in top-quark decays in pp collision data collected with the ATLAS detector at √s=7 TeV}, series = {Journal of High Energy Physics}, volume = {9}, journal = {Journal of High Energy Physics}, number = {139}, organization = {ATLAS Collaboration}, doi = {10.1007/JHEP09(2012)139}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-129152}, year = {2012}, abstract = {A search for flavour changing neutral current (FCNC) processes in top-quark decays by the ATLAS Collaboration is presented. Data collected from pp collisions at the LHC at a centre-of-mass energy of √s=7TeV during 2011, corresponding to an integrated luminosity of 2.1 fb\(^{-1}\), were used. A search was performed for top-quark pair-production events, with one top quark decaying through the t → Zq FCNC (q = u, c) channel, and the other through the Standard Model dominant mode t → W b. Only the decays of the Z boson to charged leptons and leptonic W -boson decays were considered as signal. Consequently, the final-state topology is characterised by the presence of three isolated charged leptons, at least two jets and missing transverse momentum from the undetected neutrino. No evidence for an FCNC signal was found. An upper limit on the t → Zq branching ratio of BR(t → Zq) < 0.73\% is set at the 95\% confidence level.}, language = {en} } @article{OPUS4-12916, title = {Search for charged Higgs bosons decaying via H\(^±\) → τν in \(t\overline t\) events using pp collision data at √s=7 TeV with the ATLAS detector}, series = {Journal of High Energy Physics}, volume = {06}, journal = {Journal of High Energy Physics}, number = {39}, organization = {ATLAS Collaboration}, doi = {10.1007/JHEP06(2012)039}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-129163}, year = {2012}, abstract = {The results of a search for charged Higgs bosons are presented. The analysis is based on 4.6fb\(^{-1}\) of proton-proton collision data at √s=7TeV collected by the ATLAS experiment at the Large Hadron Collider, using top quark pair events with a τ lepton in the final state. The data are consistent with the expected background from Standard Model processes. Assuming that the branching ratio of the charged Higgs boson to a τ lepton and a neutrino is 100 \%, this leads to upper limits on the branching ratio of top quark decays to a b quark and a charged Higgs boson between 5\% and 1\% for charged Higgs boson masses ranging from 90 GeV to 160 GeV, respectively. In the context of the m\(^{max}_h\) scenario of the MSSM, tan β above 12-26, as well as between 1 and 2-6, can be excluded for charged Higgs boson masses between 90 GeV and 150 GeV.}, language = {en} } @article{OPUS4-12917, title = {Search for R-parity-violating supersymmetry in events with four or more leptons in √s=7 TeV pp collisions with the ATLAS detector}, series = {Journal of High Energy Physics}, volume = {12}, journal = {Journal of High Energy Physics}, number = {124}, organization = {ATLAS Collaboration}, doi = {10.1007/JHEP12(2012)124}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-129179}, year = {2012}, abstract = {A search for new phenomena in final states with four or more leptons (electrons or muons) is presented. The analysis is based on 4.7 fb\(^{-1}\) of √s=7 TeV proton-proton collisions delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in two signal regions: one that requires moderate values of missing transverse momentum and another that requires large effective mass. The results are interpreted in a simplified model of R-parity-violating supersymmetry in which a 95\% CL exclusion region is set for charged wino masses up to 540 GeV. In an R-parity-violating MSUGRA/CMSSM model, values of m 1/2 up to 820 GeV are excluded for 10 < tan β < 40.}, language = {en} } @article{OPUS4-13985, title = {Centrality and rapidity dependence of inclusive jet production in \(\sqrt{^SNN}\)=5.02 TeV proton-lead collisions with the ATLAS detector}, series = {Physics Letters B}, volume = {748}, journal = {Physics Letters B}, organization = {ATLAS Collaboration}, doi = {10.1016/j.physletb.2015.07.023}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-139857}, pages = {392-413}, year = {2015}, abstract = {Measurements of the centrality and rapidity dependence of inclusive jet production in \(\sqrt{^SNN}\)=5.02 TeV proton-lead (p+Pb) collisions and the jet cross-section in \(\sqrt{s}\)=2.76 TeV proton-proton collisions are presented. These quantities are measured in datasets corresponding to an integrated luminosity of 27.8 nb\(^{-1}\) and 4.0 pb\(^{-1}\), respectively, recorded with the ATLAS detector at the Large Hadron Collider in 2013. The p+Pb collision centrality was characterised using the total transverse energy measured in the pseudorapidity interval -4.9<η<-3.2 in the direction of the lead beam. Results are presented for the double-differential per-collision yields as a function of jet rapidity and transverse momentum (\(p_T\)) for minimum-bias and centrality-selected p+Pb collisions, and are compared to the jet rate from the geometric expectation. The total jet yield in minimum-bias events is slightly enhanced above the expectation in a \(p_T\)-dependent manner but is consistent with the expectation within uncertainties. The ratios of jet spectra from different centrality selections show a strong modification of jet production at all \(p_T\) at forward rapidities and for large \(p_T\) at mid-rapidity, which manifests as a suppression of the jet yield in central events and an enhancement in peripheral events. These effects imply that the factorisation between hard and soft processes is violated at an unexpected level in proton-nucleus collisions. Furthermore, the modifications at forward rapidities are found to be a function of the total jet energy only, implying that the violations may have a simple dependence on the hard parton-parton kinematics.}, language = {en} } @article{OPUS4-13986, title = {Search for s-channel single top-quark production in proton-proton collisions at \(\sqrt{s}\)=8 TeV with the ATLAS detector}, series = {Physics Letters B}, volume = {740}, journal = {Physics Letters B}, organization = {ATLAS Collaboration}, doi = {10.1016/j.physletb.2014.11.042}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-139869}, pages = {118-136}, year = {2015}, abstract = {This Letter presents a search at the LHC for s-channel single top-quark production in proton-proton collisions at a centre-of-mass energy of 8 TeV. The analyzed data set was recorded by the ATLAS detector and corresponds to an integrated luminosity of 20.3 fb\(^{-1}\). Selected events contain one charged lepton, large missing transverse momentum and exactly two b-tagged jets. A multivariate event classifier based on boosted decision trees is developed to discriminate s-channel single top-quark events from the main background contributions. The signal extraction is based on a binned maximum-likelihood fit of the output classifier distribution. The analysis leads to an upper limit on the s-channel single top-quark production cross-section of 14.6 pb at the 95\% confidence level. The fit gives a cross-section of σs=5.0±4.3 pb, consistent with the Standard Model expectation.}, language = {en} } @article{OPUS4-13826, title = {Search for \(W′→t\overline {b}\) in the lepton plus jets final state in proton-proton collisions at a centre-of-mass energy of \(\sqrt {s}\)=8 TeV with the ATLAS detector}, series = {Physics Letters B}, volume = {743}, journal = {Physics Letters B}, organization = {ATLAS Collaboration}, doi = {10.1016/j.physletb.2015.02.051}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-138262}, pages = {235-255}, year = {2015}, abstract = {A search for new charged massive gauge bosons, called W′W′, is performed with the ATLAS detector at the LHC, in proton-proton collisions at a centre-of-mass energy of \(\sqrt {s}\)=8 TeV, using a dataset corresponding to an integrated luminosity of 20.3 fb\(^{-1}\). This analysis searches for W′W′ bosons in the \(W′→t\overline{b}\) decay channel in final states with electrons or muons, using a multivariate method based on boosted decision trees. The search covers masses between 0.5 and 3.0 TeV, for right-handed or left-handed W′W′ bosons. No significant deviation from the Standard Model expectation is observed and limits are set on the \(W′→t\overline{b}\) cross-section times branching ratio and on the W′W′-boson effective couplings as a function of the W′W′-boson mass using the CL\(_s\) procedure. For a left-handed (right-handed) W′W′ boson, masses below 1.70 (1.92) TeV are excluded at 95\% confidence level.}, language = {en} } @article{OPUS4-13827, title = {Search for the \(X_b\) and other hidden-beauty states in the \(π^+π^-ϒ\)(1S) channel at ATLAS}, series = {Physics Letters B}, volume = {740}, journal = {Physics Letters B}, organization = {ATLAS Collaboration}, doi = {10.1016/j.physletb.2014.11.055}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-138273}, pages = {199-217}, year = {2014}, abstract = {This Letter presents a search for a hidden-beauty counterpart of the X(3872) in the mass ranges of 10.05-10.31 GeV and 10.40-11.00 GeV, in the channel X\(_b\)→π\(^+\)π\(^-\)ϒ(1S)(→μ\(^+\)μ\(^-\)), using 16.2 fb\(^{-1}\) of s=8 TeV \(pp\) collision data collected by the ATLAS detector at the LHC. No evidence for new narrow states is found, and upper limits are set on the product of the X\(_b\) cross section and branching fraction, relative to those of the ϒ(2S), at the 95\% confidence level using the CLSCLS approach. These limits range from 0.8\% to 4.0\%, depending on mass. For masses above 10.1 GeV, the expected upper limits from this analysis are the most restrictive to date. Searches for production of the ϒ(1\(^3\)D\(_J\)), ϒ(10860), and ϒ(11020) states also reveal no significant signals.}, language = {en} } @article{OPUS4-13609, title = {Search for pair-produced long-lived neutral particles decaying to jets in the ATLAS hadronic calorimeter in pp collisions at \(\sqrt{2}\)=8 TeV}, series = {Physics Letters B}, volume = {743}, journal = {Physics Letters B}, organization = {ATLAS Collaboration}, doi = {10.1016/j.physletb.2015.02.015}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-136099}, pages = {15-34}, year = {2015}, abstract = {The ATLAS detector at the Large Hadron Collider at CERN is used to search for the decay of a scalar boson to a pair of long-lived particles, neutral under the Standard Model gauge group, in 20.3 fb-120.3 fb\(^{-1}\) of data collected in proton-proton collisions at \(\sqrt{2}\)=8 TeV. This search is sensitive to long-lived particles that decay to Standard Model particles producing jets at the outer edge of the ATLAS electromagnetic calorimeter or inside the hadronic calorimeter. No significant excess of events is observed. Limits are reported on the product of the scalar boson production cross section times branching ratio into long-lived neutral particles as a function of the proper lifetime of the particles. Limits are reported for boson masses from 100 GeV to 900 GeV, and a long-lived neutral particle mass from 10 GeV to 150 GeV.}, language = {en} } @article{OPUS4-13610, title = {Search for H→γγH→γγ produced in association with top quarks and constraints on the Yukawa coupling between the top quark and the Higgs boson using data taken at 7 TeV and 8 TeV with the ATLAS detector}, series = {Physics Letters B}, volume = {740}, journal = {Physics Letters B}, organization = {ATLAS Collaboration}, doi = {10.1016/j.physletb.2014.11.049}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-136100}, pages = {222-242}, year = {2015}, abstract = {A search is performed for Higgs bosons produced in association with top quarks using the diphoton decay mode of the Higgs boson. Selection requirements are optimized separately for leptonic and fully hadronic final states from the top quark decays. The dataset used corresponds to an integrated luminosity of 4.5 fb\(^{-1}\) of proton-proton collisions at a center-of-mass energy of 7 TeV and 20.3 fb-120.3 fb\(^{-1}\) at 8 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. No significant excess over the background prediction is observed and upper limits are set on the \(t\overline{t}H\) production cross section. The observed exclusion upper limit at 95\% confidence level is 6.7 times the predicted Standard Model cross section value. In addition, limits are set on the strength of the Yukawa coupling between the top quark and the Higgs boson, taking into account the dependence of the \(t\overline{t}H\) and tH   cross sections as well as the H→γγH→γγ branching fraction on the Yukawa coupling. Lower and upper limits at 95\% confidence level are set at -1.3 and +8.0 times the Yukawa coupling strength in the Standard Model.}, language = {en} } @article{OPUS4-13153, title = {Measurement of hard double-parton interactions in W(→ℓν) + 2-jet events at \(\sqrt{s}=7\) TeV with the ATLAS detector}, series = {New Journal of Physics}, volume = {15}, journal = {New Journal of Physics}, number = {033038}, organization = {The ATLAS Collaboration}, doi = {10.1088/1367-2630/15/3/033038}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-131531}, year = {2013}, abstract = {The production of W bosons in association with two jets in proton-proton collisions at a centre-of-mass energy of \(\sqrt{s}=7\),TeV has been analysed for the presence of double-parton interactions using data corresponding to an integrated luminosity of \(36 pb^{-1}\), collected with the ATLAS detector at the Large Hadron Collider. The fraction of events arising from double-parton interactions, \(f^D_{DP}\), has been measured through the pT balance between the two jets and amounts to \(f^D_{DP}\) = 0.08 ± 0.01 (stat.) ± 0.02 (sys.) for jets with transverse momentum \(p_T\) > 20 GeV and rapidity |y| < 2.8. This corresponds to a measurement of the effective area parameter for hard double-parton interactions of \(\sigma_{eff} = 15 ± 3 (stat.)^{+5}_{-3} (sys.)\) mb.}, language = {en} } @article{OPUS4-13154, title = {Search for extra dimensions in diphoton events from proton-proton collisions at \(\sqrt {s} = 7\)  TeV in the ATLAS detector at the LHC}, series = {New Journal of Physics}, volume = {15}, journal = {New Journal of Physics}, organization = {The ATLAS Collaboration}, doi = {10.1088/1367-2630/15/4/043007}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-131548}, pages = {043007}, year = {2013}, abstract = {The large difference between the Planck scale and the electroweak scale, known as the hierarchy problem, is addressed in certain models through the postulate of extra spatial dimensions. A search for evidence of extra spatial dimensions in the diphoton channel has been performed using the full set of proton-proton collisions at \(\sqrt {s} = 7\) TeV recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. This dataset corresponds to an integrated luminosity of \(4.9 fb^{-1}\). The diphoton invariant mass spectrum is observed to be in good agreement with the Standard Model expectation. In the context of the model proposed by Arkani-Hamed, Dimopoulos and Dvali, 95\% confidence level lower limits of between 2.52 and 3.92 TeV are set on the ultraviolet cutoff scale MS depending on the number of extra dimensions and the theoretical formalism used. In the context of the Randall-Sundrum model, a lower limit of 2.06 (1.00) TeV at 95\% confidence level is set on the mass of the lightest graviton for couplings of \(k/\overline {M}_{Pl} = 0.1 (0.01)\). Combining with the ATLAS dilepton searches based on the 2011 data, the 95\% confidence level lower limit on the Randall-Sundrum graviton mass is further tightened to 2.23 (1.03) TeV for \(k/\overline {M}_{Pl} = 0.1 (0.01)\).}, language = {en} } @article{OPUS4-12954, title = {Search for doubly charged Higgs bosons in like-sign dilepton final states at √s=7 TeV with the ATLAS detector}, series = {The European Physical Journal C}, volume = {72}, journal = {The European Physical Journal C}, number = {2244}, organization = {ATLAS Collaboration}, doi = {10.1140/epjc/s10052-012-2244-2}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-129540}, year = {2012}, abstract = {A search for doubly charged Higgs bosons decaying to pairs of electrons and/or muons is presented. The search is performed using a data sample corresponding to an integrated luminosity of 4.7 fb\(^{-1}\) of pp collisions at √s = 7 TeV collected by the ATLAS detector at the LHC. Pairs of prompt, isolated, high-p\(_T\) leptons with the same electric charge (\(e^±e^±, e^±μ^±, μ^±μ^±\)) are selected, and their invariant mass distribution is searched for a narrow resonance. No significant excess over Standard Model background expectations is observed, and limits are placed on the cross section times branching ratio for pair production of doubly charged Higgs bosons. The masses of doubly charged Higgs bosons are constrained depending on the branching ratio into these leptonic final states. Assuming pair production, coupling to left-handed fermions, and a branching ratio of 100 \% for each final state, masses below 409 GeV, 375 GeV, and 398 GeV are excluded for \(e^±e^±, e^±μ^±\), and \(μ^±μ^±\), respectively.}, language = {en} } @article{OPUS4-12955, title = {A search for \(t\overline t\) resonances in lepton+jets events with highly boosted top quarks collected in pp collisions at √s=7 TeV with the ATLAS detector}, series = {Journal of High Energy Physics}, volume = {09}, journal = {Journal of High Energy Physics}, number = {41}, organization = {ATLAS Collaboration}, doi = {10.1007/JHEP09(2012)041}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-129555}, year = {2012}, abstract = {A search for resonant production of high-mass top-quark pairs is performed on 2.05 fb\(^{-1}\) of proton-proton collisions at √s=7 TeV collected in 2011 with the ATLAS experiment at the Large Hadron Collider. This analysis of the lepton+jets final state is specifically designed for the particular topology that arises from the decay of highly boosted top quarks. The observed \(t\overline t\) invariant mass spectrum is found to be compatible with the Standard Model prediction and 95\% credibility level upper limits are derived on the \(t\overline t\) production rate through new massive states. An upper limit of 0.7 pb is set on the production cross section times branching fraction of a narrow 1 TeV resonance. A Kaluza-Klein gluon with a mass smaller than 1.5 TeV is excluded.}, language = {en} } @article{OPUS4-12956, title = {Search for light scalar top-quark pair production in final states with two leptons with the ATLAS detector in √s=7 TeV proton-proton collisions}, series = {The European Physical Journal C}, volume = {72}, journal = {The European Physical Journal C}, number = {2237}, organization = {ATLAS Collaboration}, doi = {10.1140/epjc/s10052-012-2237-1}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-129561}, year = {2012}, abstract = {A search is presented for the pair production of light scalar top quarks in √s=7 TeV proton-proton collisions recorded with the ATLAS detector at the Large Hadron Collider. This analysis uses the full data sample collected during 2011 running that corresponds to a total integrated luminosity of 4.7 fb\(^{-1}\). Light scalar top quarks are searched for in events with two opposite-sign leptons (e, μ), large missing transverse momentum and at least one jet in the final state. No excess over Standard Model expectations is found, and the results are interpreted under the assumption that the light scalar top decays to a b-quark in addition to an on-shell chargino whose decay occurs through a virtual W boson. If the chargino mass is 106 GeV, light scalar top-quark masses up to 130 GeV are excluded for neutralino masses below 70 GeV.}, language = {en} } @article{OPUS4-12888, title = {ATLAS search for a heavy gauge boson decaying to a charged lepton and a neutrino in pp collisions at √s=7 TeV}, series = {The European Physical Journal C}, volume = {72}, journal = {The European Physical Journal C}, number = {2241}, organization = {ATLAS Collaboration}, doi = {10.1140/epjc/s10052-012-2241-5}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-128888}, year = {2012}, abstract = {The ATLAS detector at the LHC is used to search for high-mass states, such as heavy charged gauge bosons (W′), decaying to a charged lepton (electron or muon) and a neutrino. Results are presented based on the analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 4.7 fb\(^{-1}\). No excess beyond Standard Model expectations is observed. A W′ with Sequential Standard Model couplings is excluded at the 95 \% credibility level for masses up to 2.55 TeV. Excited chiral bosons (W∗) with equivalent coupling strength are excluded for masses up to 2.42 TeV.}, language = {en} } @article{OPUS4-12889, title = {Search for supersymmetry in events with large missing transverse momentum, jets, and at least one tau lepton in 7 TeV proton-proton collision data with the}, series = {The European Physical Journal C}, volume = {72}, journal = {The European Physical Journal C}, number = {2215}, organization = {ATLAS Collaboration}, doi = {dx.doi.org/10.1140/epjc/s10052-012-2215-7}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-128891}, year = {2012}, abstract = {A search for supersymmetry (SUSY) in events with large missing transverse momentum, jets, and at least one hadronically decaying τ lepton, with zero or one additional light lepton (e/μ), has been performed using 4.7 fb\(^{-1}\) of proton-proton collision data at \(\sqrt s\)=7TeV recorded with the ATLAS detector at the Large Hadron Collider. No excess above the Standard Model background expectation is observed and a 95 \% confidence level visible cross-section upper limit for new phenomena is set. In the framework of gauge-mediated SUSY-breaking models, lower limits on the mass scale Λ are set at 54 TeV in the regions where the \(\tilde τ_1\) is the next-to-lightest SUSY particle (tanβ>20). These limits provide the most stringent tests to date of GMSB models in a large part of the parameter space considered.}, language = {en} } @article{OPUS4-12890, title = {Measurement of the charge asymmetry in top quark pair production in pp collisions at √s=7 TeV using the ATLAS detector}, series = {The European Physical Journal C}, volume = {72}, journal = {The European Physical Journal C}, number = {2039}, organization = {ATLAS Collaboration}, doi = {10.1140/epjc/s10052-012-2039-5}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-128904}, year = {2012}, abstract = {A measurement of the top-antitop production charge asymmetry A C is presented using data corresponding to an integrated luminosity of 1.04 fb\(^{-1}\) of pp collisions at √s=7 TeV collected by the ATLAS detector at the LHC. Events are selected with a single lepton (electron or muon), missing transverse momentum and at least four jets of which at least one jet is identified as coming from a b-quark. A kinematic fit is used to reconstruct the t\(\overline t\) event topology. After background subtraction, a Bayesian unfolding procedure is performed to correct for acceptance and detector effects. The measured value of A\(_C\) is AC=-0.019±0.028 (stat.)±0.024 (syst.), consistent with the prediction from the MC@NLO Monte Carlo generator of A\(_C\) =0.006±0.002. Measurements of A\(_C\) in two ranges of invariant mass of the top-antitop pair are also shown.}, language = {en} } @article{OPUS4-12891, title = {Measurement of the top quark mass with the template method in the \(t\overline t\)→lepton+jets channel using ATLAS data}, series = {The European Physical Journal C}, volume = {72}, journal = {The European Physical Journal C}, number = {2046}, organization = {ATLAS Collaboration}, doi = {10.1140/epjc/s10052-012-2046-6}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-128912}, year = {2012}, abstract = {The top quark mass has been measured using the template method in the \(t\overline t\)→lepton+jets channel based on data recorded in 2011 with the ATLAS detector at the LHC. The data were taken at a proton-proton centre-of-mass energy of √s=7 TeV and correspond to an integrated luminosity of 1.04 fb\(^{-1}\). The analyses in the e+jets and μ+jets decay channels yield consistent results. The top quark mass is measured to be m\(_{top}\)=174.5±0.6\(_{stat}\)±2.3\(_{syst}\) GeV.}, language = {en} } @article{OPUS4-12892, title = {Measurement of the cross section for top-quark pair production in pp collisions at √s=7TeV with the ATLAS detector using final states with two high-p\(_T\) leptons}, series = {Journal of High Energy Physics}, volume = {5}, journal = {Journal of High Energy Physics}, number = {59}, organization = {ATLAS Collaboration}, doi = {10.1007/JHEP05(2012)059}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-128924}, year = {2012}, abstract = {A measurement is reported of the production cross section of top-quark pairs (\(t\overline t\)) in proton-proton collisions at a center-of-mass energy of 7 TeV recorded with the ATLAS detector at the LHC. Candidate events have a signature consistent with containing two isolated leptons, large missing transverse momentum, and at least two jets. Using a data sample corresponding to an integrated luminosity of 0.70 fb\(^{-1}\), a \(t\overline t\) production cross section σ\(_{t\overline t}\)=176±5(stat.)\(^{+14}_{-11}\)(syst.)±8(lum.) pb is measured for an assumed top-quark mass of m\(_t\)  = 172.5 GeV. This measurement is in good agreement with Standard Model predictions.}, language = {en} } @article{OPUS4-12893, title = {Measurement of \(t\overline t\) production with a veto on additional central jet activity in pp collisions at √s=7 TeV using the ATLAS detector}, series = {European Physical Journal C}, volume = {72}, journal = {European Physical Journal C}, number = {2043}, organization = {ATLAS Collaboration}, doi = {10.1140/epjc/s10052-012-2043-9}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-128931}, year = {2012}, abstract = {A measurement of the jet activity in \(t\overline t\) events produced in proton-proton collisions at a centre-of-mass energy of 7 TeV is presented, using 2.05 fb\(^{-1}\) of integrated luminosity collected by the ATLAS detector at the Large Hadron Collider. The \(t\overline t\) events are selected in the dilepton decay channel with two identified b-jets from the top quark decays. Events are vetoed if they contain an additional jet with transverse momentum above a threshold in a central rapidity interval. The fraction of events surviving the jet veto is presented as a function of this threshold for four different central rapidity interval definitions. An alternate measurement is also performed, in which events are vetoed if the scalar transverse momentum sum of the additional jets in each rapidity interval is above a threshold. In both measurements, the data are corrected for detector effects and compared to the theoretical models implemented in MC@NLO, Powheg, Alpgen and Sherpa. The experimental uncertainties are often smaller than the spread of theoretical predictions, allowing deviations between data and theory to be observed in some regions of phase space.}, language = {en} } @article{OPUS4-13155, title = {Search for excited electrons and muons in \(\sqrt {s}=8\) TeV proton-proton collisions with the ATLAS detector}, series = {New Journal of Physics}, volume = {15}, journal = {New Journal of Physics}, number = {093011}, organization = {The ATLAS Collaboration}, doi = {10.1088/1367-2630/15/9/093011}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-131557}, year = {2013}, abstract = {The ATLAS detector at the Large Hadron Collider is used to search for excited electrons and excited muons in the channel \(pp →ℓℓ^\ast→ℓℓ\gamma \), assuming that excited leptons are produced via contact interactions. The analysis is based on \(13 fb^{-1}\) of pp collisions at a centre-of-mass energy of 8 TeV. No evidence for excited leptons is found, and a limit is set at the 95\% credibility level on the cross section times branching ratio as a function of the excitedlepton mass \(m_{ℓ^\ast}\) . For \(m_{ℓ^\ast}\) ≽0.8 TeV, the respective upper limits on \(\sigma B(ℓ→ ℓ\gamma)\) are 0.75 and 0.90 fb for the \(e^\ast\) and \(μ^\ast\) searches. Limits on \(\sigma B\) are converted into lower bounds on the compositeness scale \(\Lambda\). In the special case where \(\Lambda = m_{ℓ^\ast}\), excited-electron and excited-muon masses below 2.2 TeV are excluded.}, language = {en} } @article{OPUS4-13156, title = {Search for WH production with a light Higgs boson decaying to prompt electron-jets in proton-proton collisions at \(\sqrt {s}=7\)  TeV with the ATLAS detector}, series = {New Journal of Physics}, volume = {15}, journal = {New Journal of Physics}, number = {043009}, organization = {The ATLAS Collaboration}, doi = {10.1088/1367-2630/15/4/043009}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-131565}, year = {2013}, abstract = {A search is performed for WH production with a light Higgs boson decaying to hidden-sector particles resulting in clusters of collimated electrons, known as electron-jets. The search is performed with \(2.04 fb^{-1}\) of data collected in 2011 with the ATLAS detector at the Large Hadron Collider in proton-proton collisions at \(\sqrt {s}=7 TeV\) . One event satisfying the signal selection criteria is observed, which is consistent with the expected background rate. Limits on the product of the WH production cross section and the branching ratio of a Higgs boson decaying to prompt electron-jets are calculated as a function of a Higgs boson mass in the range from 100 to 140 GeV.}, language = {en} } @article{OPUS4-12959, title = {Hunt for new phenomena using large jet multiplicities and missing transverse momentum with ATLAS in 4.7 fb\(^{-1}\) of √s=7TeV proton-proton collisions}, series = {The Journal of High Energy Physics}, volume = {07}, journal = {The Journal of High Energy Physics}, number = {167}, organization = {ATLAS Collaboration}, doi = {10.1007/JHEP07(2012)167}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-129591}, year = {2012}, abstract = {Results are presented of a search for new particles decaying to large numbers of jets in association with missing transverse momentum, using 4.7 fb\(^{-1}\) of pp collision data at √s=7TeV collected by the ATLAS experiment at the Large Hadron Collider in 2011. The event selection requires missing transverse momentum, no isolated electrons or muons, and from ≥6 to ≥9 jets. No evidence is found for physics beyond the Standard Model. The results are interpreted in the context of a MSUGRA/CMSSM supersymmetric model, where, for large universal scalar mass m 0, gluino masses smaller than 840 GeV are excluded at the 95\% confidence level, extending previously published limits. Within a simplified model containing only a gluino octet and a neutralino, gluino masses smaller than 870 GeV are similarly excluded for neutralino masses below 100 GeV.}, language = {en} } @article{OPUS4-12895, title = {Search for second generation scalar leptoquarks in pp collisions at √s=7 TeV with the ATLAS detector}, series = {The European Physical Journal C}, volume = {72}, journal = {The European Physical Journal C}, number = {2151}, organization = {ATLAS Collaboration}, doi = {10.1140/epjc/s10052-012-2151-6}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-128957}, year = {2012}, abstract = {The results of a search for the production of second generation scalar leptoquarks are presented for final states consisting of either two muons and at least two jets or a muon plus missing transverse momentum and at least two jets. A total of 1.03 fb\(^{-1}\) integrated luminosity of proton-proton collision data produced by the Large Hadron Collider at s√=7 TeV and recorded by the ATLAS detector is used for the search. The event yields in the signal regions are found to be consistent with the Standard Model background expectations. The production of second generation leptoquarks is excluded for a leptoquark mass m\(_{LQ}\)<594 (685) GeV at 95 \% confidence level, for a branching ratio of 0.5 (1.0) for leptoquark decay to a muon and a quark.}, language = {en} } @article{OPUS4-12896, title = {Search for same-sign top-quark production and fourth-generation down-type quarks in pp collisions at √s=7 TeV with the ATLAS detector}, series = {Journal of High Energy Physics}, volume = {04}, journal = {Journal of High Energy Physics}, number = {69}, organization = {ATLAS Collaboration}, doi = {10.1007/JHEP04(2012)069}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-128960}, year = {2012}, abstract = {A search is presented for same-sign top-quark production and down-type heavy quarks of charge -1/3 in events with two isolated leptons (e or μ) that have the same electric charge, at least two jets and large missing transverse momentum. The data are selected from pp collisions at √s=7TeV recorded by the ATLAS detector and correspond to an integrated luminosity of 1.04 fb\(^{-1}\). The observed data are consistent with expectations from Standard Model processes. Upper limits are set at 95 \% confidence level on the cross section of new sources of same-sign top-quark pair production of 1.4-2.0 pb depending on the assumed mediator mass. Upper limits are also set on the pair-production cross-section for new heavy down-type quarks; a lower limit of 450 GeV is set at 95 \% confidence level on the mass of heavy down-type quarks under the assumption that they decay 100 \% of the time to W t.}, language = {en} } @article{OPUS4-12897, title = {Jet mass and substructure of inclusive jets in √s=7 TeV pp collisions with the ATLAS experiment}, series = {Journal of High Energy Physics}, volume = {05}, journal = {Journal of High Energy Physics}, number = {128}, organization = {ATLAS Collaboration}, doi = {10.1007/JHEP05(2012)128}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-128970}, year = {2012}, abstract = {Recent studies have highlighted the potential of jet substructure techniques to identify the hadronic decays of boosted heavy particles. These studies all rely upon the assumption that the internal substructure of jets generated by QCD radiation is well understood. In this article, this assumption is tested on an inclusive sample of jets recorded with the ATLAS detector in 2010, which corresponds to 35 pb\(^{-1}\) of pp collisions delivered by the LHC at √s=7TeV. In a subsample of events with single pp collisions, measurements corrected for detector efficiency and resolution are presented with full systematic uncertainties. Jet invariant mass, k\(_t\) splitting scales and N-subjettiness variables are presented for anti-k\(_t\) R = 1.0 jets and Cambridge-Aachen R = 1.2 jets. Jet invariant-mass spectra for Cambridge-Aachen R = 1.2 jets after a splitting and filtering procedure are also presented. Leading-order parton-shower Monte Carlo predictions for these variables are found to be broadly in agreement with data. The dependence of mean jet mass on additional pp interactions is also explored.}, language = {en} } @article{OPUS4-22578, title = {Search for diboson resonances with boson-tagged jets in \({pp}\) collisions at root S=13 TeV with the ATLAS detector}, series = {Physics Letters B}, volume = {777}, journal = {Physics Letters B}, organization = {The ATLAS Collaboration}, doi = {10.1016/j.physletb.2017.12.011}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-225782}, pages = {91-113}, year = {2018}, abstract = {Narrow resonances decaying into WW, WZ or ZZ boson pairs are searched for in 36.7 fb(-1) of proton-proton collision data at a centre-of-mass energy of root s = 13 TeV recorded with the ATLAS detector at the Large Hadron Collider in 2015 and 2016. The diboson system is reconstructed using pairs of large-radius jets with high transverse momentum and tagged as compatible with the hadronic decay of high-momentum Wor Zbosons, using jet mass and substructure properties. The search is sensitive to diboson resonances with masses in the range 1.2-5.0 TeV. No significant excess is observed in any signal region. Exclusion limits are set at the 95\% confidence level on the production cross section times branching ratio to dibosons for a range of theories beyond the Standard Model. Model-dependent lower limits on the mass of new gauge bosons are set, with the highest limit set at 3.5 TeV in the context of mass-degenerate resonances that couple predominantly to bosons. (c) 2017 The Author(s). Published by Elsevier B.V.}, language = {en} } @article{OPUS4-22540, title = {Measurement of the production cross-section of a single top quark in association with a \(Z\) boson in proton-proton collisions at 13 TeV with the ATLAS detector}, series = {Physics letters B}, volume = {780}, journal = {Physics letters B}, organization = {The ATLAS Collaboration}, doi = {10.1016/j.physletb.2018.03.023}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-225406}, pages = {557-577}, year = {2018}, abstract = {The production of a top quark in association with a Z boson is investigated. The proton-proton collision data collected by the ATLAS experiment at the LHC in 2015 and 2016 at a centre-of-mass energy of root s = 13 TeV are used, corresponding to an integrated luminosity of 36.1 fb(-1). Events containing three identified leptons (electrons and/or muons) and two jets, one of which is identified as a b-quark jet are selected. The major backgrounds are diboson, tt(\$)over-bar and Z + jets production. A neural network is used to improve the background rejection and extract the signal. The resulting significance is 4.2 sigma in the data and the expected significance is 5.4 sigma. The measured cross-section for tZq production is 600 +/- 170(stat.)+/- 140(syst.)fb. (C) 2018 The Author(s). Published by Elsevier B.V.}, language = {en} } @article{OPUS4-22543, title = {A search for resonances decaying into a Higgs boson and a new particle \(X\) in the \({XH}\) -> \({qqbb}\) final state with the ATLAS detector}, series = {Physics letters B}, volume = {779}, journal = {Physics letters B}, organization = {The ATLAS Collaboration}, doi = {10.1016/j.physletb.2018.01.042}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-225435}, pages = {24-45}, year = {2018}, abstract = {A search for heavy resonances decaying into a Higgs boson (H) and a new particle (X) is reported, utilizing 36.1 fb(-1) of proton-proton collision data at root s = 13 TeV collected during 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider. The particle Xis assumed to decay to a pair of light quarks, and the fully hadronic final state XH -> q (q) over bar 'b (b) over bar is analysed. The search considers the regime of high XH resonance masses, where the X and H bosons are both highly Lorentz-boosted and are each reconstructed using a single jet with large radius parameter. A two-dimensional phase space of XH mass versus X mass is scanned for evidence of a signal, over a range of XH resonance mass values between 1 TeV and 4 TeV, and for X particles with masses from 50 GeV to 1000 GeV. All search results are consistent with the expectations for the background due to Standard Model processes, and 95\% CL upper limits are set, as a function of XH and X masses, on the production cross-section of the XH -> q (q) over bar 'b (b) over bar resonance. (c) 2018 The Author(s). Published by Elsevier B.V.}, language = {en} } @article{OPUS4-22594, title = {Search for an invisibly decaying Higgs boson or dark matter candidates produced in association with a Z boson in \({pp}\) collisions at root s=13 TeV with the ATLAS detector}, series = {Physics Letters B}, volume = {776}, journal = {Physics Letters B}, number = {1}, organization = {The ATLAS Collaboration}, doi = {10.1016/j.physletb.2017.11.049}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-225947}, pages = {318-337}, year = {2018}, abstract = {A search for an invisibly decaying Higgs boson or dark matter candidates produced in association with a leptonically decaying Z boson in proton-proton collisions at root s = 13 TeV is presented. This search uses 36.1 fb(-1) of data collected by the ATLAS experiment at the Large Hadron Collider. No significant deviation from the expectation of the Standard Model backgrounds is observed. Assuming the Standard Model ZH production cross-section, an observed (expected) upper limit of 67\% (39\%) at the 95\% confidence level is set on the branching ratio of invisible decays of the Higgs boson with mass m(H) = 125 GeV. The corresponding limits on the production cross-section of the ZH process with the invisible Higgs boson decays are also presented. Furthermore, exclusion limits on the dark matter candidate and mediator masses are reported in the framework of simplified dark matter models. (c) 2017 The Author(s). Published by Elsevier B.V.}, language = {en} } @article{OPUS4-22544, title = {Search for heavy resonances decaying into a W or Z boson and a Higgs boson in final states with leptons and b-jets in 36 fb\(^{-1}\) of root s=13 TeV pp collisions with the ATLAS detector}, series = {Journal of High Energy Physics}, volume = {174}, journal = {Journal of High Energy Physics}, number = {3}, organization = {The ATLAS collaboration}, doi = {10.1007/JHEP03(2018)174}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-225446}, pages = {1-52}, year = {2018}, abstract = {A search is conducted for new resonances decaying into a W or Z boson and a 125 GeV Higgs boson in the nu(nu) over barb (b) over bar, l(+/-)nu b (b) over bar, and l(+)l(-)b (b) over bar final states, where l(+/-) = e(+/-) or mu(+/-), in pp collisions at root s = 13 TeV. The data used correspond to a total integrated luminosity of 36.1 fb(-1) collected with the ATLAS detector at the Large Hadron Collider during the 2015 and 2016 data-taking periods. The search is conducted by examining the reconstructed invariant or transverse mass distributions of Wh and Zh candidates for evidence of a localised excess in the mass range of 220 GeV up to 5 TeV. No significant excess is observed and the results are interpreted in terms of constraints on the production cross-section times branching fraction of heavy W' and Z' resonances in heavy-vector-triplet models and the CP-odd scalar boson A in two-Higgs-doublet models. Upper limits are placed at the 95\% confidence level and range between 9.0 x 10(-4) pb and 7.3 x 10(-1) pb depending on the model and mass of the resonance.}, language = {en} } @article{OPUS4-22070, title = {Search for supersymmetry in events with four or more leptons in root s=13 TeV \({pp}\) collisions with ATLAS}, series = {Physical Review D}, volume = {98}, journal = {Physical Review D}, number = {3}, organization = {The ATLAS Collaboration}, doi = {10.1103/PhysRevD.98.032009}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-220705}, pages = {1-31}, year = {2018}, abstract = {Results from a search for supersymmetry in events with four or more charged leptons (electrons, muons and taus) are presented. The analysis uses a data sample corresponding to 36.1 fb(-1) of proton-proton collisions delivered by the Large Hadron Collider at root s = 13 TeV and recorded by the ATLAS detector. Four-lepton signal regions with up to two hadronically decaying taus are designed to target a range of supersymmetric scenarios that can be either enriched in or depleted of events involving the production and decay of a Z boson. Data yields are consistent with Standard Model expectations and results are used to set upper limits on the event yields from processes beyond the Standard Model. Exclusion limits are set at the 95\% confidence level in simplified models of general gauge mediated supersymmetry, where Higgsino masses are excluded up to 295 GeV. In R-parity-violating simplified models with decays of the lightest supersymmetric particle to charged leptons, lower limits of 1.46, 1.06, and 2.25 TeV are placed on wino, slepton and gluino masses, respectively.}, language = {en} } @article{OPUS4-22562, title = {Measurement of long-range multiparticle azimuthal correlations with the subevent cumulant method in \({pp}\) and \(p\)+Pb collisions with the ATLAS detector at the CERN Large Hadron Collider}, series = {Physical Review C}, volume = {97}, journal = {Physical Review C}, number = {2}, organization = {The ATLAS Collaboration}, doi = {10.1103/PhysRevC.97.024904}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-225623}, pages = {024904, 1-25}, year = {2018}, abstract = {A detailed study of multiparticle azimuthal correlations is presented using pp data at root s = 5.02 and 13 TeV, and p+Pb data at root s(NN) = 5.02 TeV, recorded with the ATLAS detector at the CERN Large Hadron Collider. The azimuthal correlations are probed using four-particle cumulants c(n){4} and flow coefficients v(n){4} = (-c(n){4})(1/4) for n = 2 and 3, with the goal of extracting long-range multiparticle azimuthal correlation signals and suppressing the short-range correlations. The values of c(n){4} are obtained as a function of the average number of charged particles per event, < N-ch >, using the recently proposed two-subevent and three-subevent cumulant methods, and compared with results obtained with the standard cumulant method. The standard method is found to be strongly biased by short-range correlations, which originate mostly from jetswith a positive contribution to c(n){4}. The threesubevent method, on the other hand, is found to be least sensitive to short-range correlations. The three-subevent method gives a negative c(2){4}, and therefore a well-defined v(2){4}, nearly independent of < N-ch >, which implies that the long-range multiparticle azimuthal correlations persist to events with low multiplicity. Furthermore, v(2){4} is found to be smaller than the v(2){2} measured using the two-particle correlation method, as expected for long-range collective behavior. Finally, the measured values of v(2){4} and v(2){2} are used to estimate the number of sources relevant for the initial eccentricity in the collision geometry. The results based on the subevent cumulant technique provide direct evidence, in small collision systems, for a long-range collectivity involving many particles distributed across a broad rapidity interval.}, language = {en} } @article{OPUS4-22087, title = {Measurement of differential cross sections and W\(^+\)/W\(^-\) cross-section ratios for W boson production in association with jets at root s=8 TeV with the ATLAS detector}, series = {Journal of High Energy Physics}, volume = {77}, journal = {Journal of High Energy Physics}, number = {5}, organization = {The ATLAS collaboration}, doi = {10.1007/JHEP05(2018)077}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-220872}, pages = {1-61}, year = {2018}, abstract = {This paper presents a measurement of the W boson production cross section and the W+/W- cross-section ratio, both in association with jets, in proton-proton collisions at root s = 8 TeV with the ATLAS experiment at the Large Hadron Collider. The measurement is performed in final states containing one electron and missing transverse momentum using data corresponding to an integrated luminosity of 20.2 fb(-1). Differential cross sections for events with at least one or two jets are presented for a range of observables, including jet transverse momenta and rapidities, the scalar sum of transverse momenta of the visible particles and the missing transverse momentum in the event, and the transverse momentum of the W boson. For a subset of the observables, the differential cross sections of positively and negatively charged W bosons are measured separately. In the cross-section ratio of W+/W- the dominant systematic uncertainties cancel out, improving the measurement precision by up to a factor of nine. The observables and ratios selected for this paper provide valuable input for the up quark, down quark, and gluon parton distribution functions of the proton.}, language = {en} } @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{OPUS4-15016, title = {Search for production of WW/WZ resonances decaying to a lepton, neutrino and jets in pp collisions at \(\sqrt {s}\)= 8 TeV with the ATLAS detector}, series = {European Physical Journal C: Particles and Fields}, volume = {75}, journal = {European Physical Journal C: Particles and Fields}, number = {5}, organization = {ATLAS Collaboration}, doi = {10.1140/epjc/s10052-015-3425-6}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-150164}, pages = {209}, year = {2015}, abstract = {A search is presented for narrow diboson resonances decaying to WW or WZ in the final state where one W boson decays leptonically (to an electron or a muon plus a neutrino) and the other W/Z boson decays hadronically. The analysis is performed using an integrated luminosity of 20.3 fb\(^{-1}\) of pp collisions at \(\sqrt {s}\) = 8 TeV collected by the ATLAS detector at the large hadron collider. No evidence for resonant diboson production is observed, and resonance masses below 700 and 1490 GeV are excluded at 95 \% confidence level for the spin-2 Randall-Sundrum bulk graviton G\(^{*}\) with coupling constant of 1.0 and the extended gauge model W′ boson respectively.}, language = {en} } @article{OPUS4-14990, title = {Measurement of the top-quark mass in the fully hadronic decay channel from ATLAS data at \(\sqrt {s}\)=7TeV}, series = {European Physical Journal C: Particles and Fields}, volume = {75}, journal = {European Physical Journal C: Particles and Fields}, number = {4}, organization = {ATLAS Collaboration}, doi = {10.1140/epjc/s10052-015-3373-1}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-149905}, pages = {158}, year = {2015}, abstract = {The mass of the top quark is measured in a data set corresponding to 4.6  fb\(^{-1}\) of proton-proton collisions with centre-of-mass energy \(\sqrt {s}\)=7 TeV collected by the ATLAS detector at the LHC. Events consistent with hadronic decays of top-antitop quark pairs with at least six jets in the final state are selected. The substantial background from multijet production is modelled with data-driven methods that utilise the number of identified b-quark jets and the transverse momentum of the sixth leading jet, which have minimal correlation. The top-quark mass is obtained from template fits to the ratio of three-jet to dijet mass. The three-jet mass is calculated from the three jets produced in a top-quark decay. Using these three jets the dijet mass is obtained from the two jets produced in the W boson decay. The top-quark mass obtained from this fit is thus less sensitive to the uncertainty in the energy measurement of the jets. A binned likelihood fit yields a top-quark mass of m\(_{t}\)= 175.1 ± 1.4 (stat.) ± 1.2 (syst.) GeV.}, language = {en} } @article{OPUS4-22083, title = {Search for squarks and gluinos in final states with jets and missing transverse momentum using 36 fb\(^{-1}\) of root s=13 TeV \({pp}\) collision data with the ATLAS detector}, series = {Physical Review D}, volume = {97}, journal = {Physical Review D}, number = {11}, organization = {The ATLAS Collaboration}, doi = {10.1103/PhysRevD.97.112001}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-220835}, pages = {1-47}, year = {2018}, abstract = {A search for the supersymmetric partners of quarks and gluons (squarks and gluinos) in final states containing hadronic jets and missing transverse momentum, but no electrons or muons, is presented. The data used in this search were recorded in 2015 and 2016 by the ATLAS experiment in root s = 13 TeV proton-proton collisions at the Large Hadron Collider, corresponding to an integrated luminosity of 36.1 fb(-1). The results are interpreted in the context of various models where squarks and gluinos are pair produced and the neutralino is the lightest supersymmetric particle. An exclusion limit at the 95\% confidence level on the mass of the gluino is set at 2.03 TeV for a simplified model incorporating only a gluino and the lightest neutralino, assuming the lightest neutralino is massless. For a simplified model involving the strong production of mass-degenerate first-and second-generation squarks, squark masses below 1.55 TeVare excluded if the lightest neutralino is massless. These limits substantially extend the region of supersymmetric parameter space previously excluded by searches with the ATLAS detector.}, language = {en} } @article{OPUS4-22584, title = {\({ZZ}\) -> l(+)l(-)l '(+)l '(-) cross-section measurements and search for anomalous triple gauge couplings in 13 TeV \({pp}\) collisions with the ATLAS detector}, series = {Physical Review D}, volume = {97}, journal = {Physical Review D}, number = {3}, organization = {The ATLAS Collaboration}, doi = {10.1103/PhysRevD.97.032005}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-225844}, pages = {1-39}, year = {2018}, abstract = {Measurements of ZZ production in the l(+)l(-)l'(+)l'(-) channel in proton-proton collisions at 13 TeV center-of-mass energy at the Large Hadron Collider are presented. The data correspond to 36.1 fb(-1) of collisions collected by the ATLAS experiment in 2015 and 2016. Here l and l ' stand for electrons or muons. Integrated and differential ZZ -> l(+)l(-)l'(+)l'(-) cross sections with Z -> l(+)l(-) candidate masses in the range of 66 GeV to 116 GeV are measured in a fiducial phase space corresponding to the detector acceptance and corrected for detector effects. The differential cross sections are presented in bins of twenty observables, including several that describe the jet activity. The integrated cross section is also extrapolated to a total phase space and to all standard model decays of Z bosons with mass between 66 GeV and 116 GeV, resulting in a value of 17.3 +/- 0.9 [+/- 0.6(start) +/- 0.5 (syst) +/- 0.6 (lumi)] pb. The measurements are found to be in good agreement with the standard model. A search for neutral triple gauge couplings is performed using the transverse momentum distribution of the leading Z boson candidate. No evidence for such couplings is found and exclusion limits are set on their parameters.}, language = {en} } @article{OPUS4-22586, title = {Search for \(B\) - \(L\) \(R\)-parity-violating top squarks in root s=13 TeV \({pp}\) collisions with the ATLAS experiment}, series = {Physical Review D}, volume = {97}, journal = {Physical Review D}, number = {3}, organization = {The ATLAS Collaboration}, doi = {10.1103/PhysRevD.97.032003}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-225863}, pages = {1-42}, year = {2018}, abstract = {A search is presented for the direct pair production of the stop, the supersymmetric partner of the top quark, that decays through an R-parity-violating coupling to a final state with two leptons and two jets, at least one of which is identified as a b-jet. The data set corresponds to an integrated luminosity of 36.1 fb(-1) of proton-proton collisions at a center-of-mass energy of root s = 13 TeV, collected in 2015 and 2016 by the ATLAS detector at the LHC. No significant excess is observed over the Standard Model background, and exclusion limits are set on stop pair production at a 95\% confidence level. Lower limits on the stop mass are set between 600 GeV and 1.5 TeV for branching ratios above 10\% for decays to an electron or muon and a b-quark.}, language = {en} } @article{OPUS4-31955, title = {Search for light resonances decaying to boosted quark pairs and produced in association with a photon or a jet in proton-proton collisions at root s=13 TeV with the ATLAS detector}, series = {Physics Letters B}, volume = {788}, journal = {Physics Letters B}, organization = {The ATLAS Collaboration}, doi = {10.1016/j.physletb.2018.09.062}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-319552}, pages = {316-335}, year = {2019}, abstract = {This Letter presents a search for new light resonances decaying to pairs of quarks and produced in association with a high-p(T) photon or jet. The dataset consists of proton-proton collisions with an integrated luminosity of 36.1 fb(-1) at a centre-of-mass energy of root s = 13 TeV recorded by the ATLAS detector at the Large Hadron Collider. Resonance candidates are identified as massive large-radius jets with substructure consistent with a particle decaying into a quark pair. The mass spectrum of the candidates is examined for local excesses above background. No evidence of a new resonance is observed in the data, which are used to exclude the production of a lepto-phobic axial-vector Z' boson. (C) 2018 The Author(s). Published by Elsevier B.V.}, language = {en} } @article{OPUS4-22541, title = {Measurement of the cross section for isolated-photon plus jet production in \({pp}\) collisions at root s=13 TeV using the ATLAS detector}, series = {Physics Letters B}, volume = {780}, journal = {Physics Letters B}, organization = {The ATLAS Collaboration}, doi = {10.1016/j.physletb.2018.03.035}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-225412}, pages = {578-602}, year = {2018}, abstract = {The dynamics of isolated-photon production in association with a jet in proton-proton collisions at a centre-of-mass energy of 13 TeV are studied with the ATLAS detector at the LHC using a dataset with an integrated luminosity of 3.2 fb(-1). Photons are required to have transverse energies above 125 GeV. Jets are identified using the anti-k(t) algorithm with radius parameter R = 0.4 and required to have transverse momenta above 100 GeV. Measurements of isolated-photon plus jet cross sections are presented as functions of the leading-photon transverse energy, the leading-jet transverse momentum, the azimuthal angular separation between the photon and the jet, the photon-jet invariant mass and the scattering angle in the photon-jet centre-of-mass system. Tree-level plus parton-shower predictions from SHERPA and PYTHIA as well as next-to-leading-order QCD predictions from JETPHOX and SHERPA are compared to the measurements. (C) 2018 The Author. Published by Elsevier B.V.}, language = {en} } @article{OPUS4-22582, title = {Measurement of the exclusive gamma gamma -> mu\(^+\)mu\(^-\) process in proton-proton collisions at root s=13 TeV with the ATLAS detector}, series = {Physics Letters B}, volume = {777}, journal = {Physics Letters B}, organization = {The ATLAS Collaboration}, doi = {10.1016/j.physletb.2017.12.043}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-225825}, pages = {303-323}, year = {2018}, abstract = {The production of exclusive gamma gamma -> mu(+)mu(-) events in proton-proton collisions at a centre-of-mass energy of 13 TeV is measured with the ATLAS detector at the LHC, using data corresponding to an integrated luminosity of 3.2 fb(-1). The measurement is performed for a dimuon invariant mass of 12 GeV < m(mu+mu-) < 70 GeV. The integrated cross-section is determined within a fiducial acceptance region of the ATLAS detector and differential cross-sections are measured as a function of the dimuon invariant mass. The results are compared to theoretical predictions both with and without corrections for absorptive effects. (c) 2017 The Author(s). Published by Elsevier B.V.}, language = {en} }