@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{OPUS4-12956, 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{OPUS4-12955, 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{OPUS4-12954, 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{OPUS4-12917, 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{OPUS4-12916, 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{OPUS4-12897, 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{OPUS4-12896, 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{OPUS4-12895, 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{OPUS4-12893, 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{OPUS4-12892, 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{OPUS4-12891, 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{OPUS4-12890, 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{OPUS4-12915, 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{OPUS4-12889, 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{OPUS4-12888, 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{OPUS4-12813, title = {Search for pair production of massive particles decaying into three quarks with the ATLAS detector in √s=7TeV pp collisions at the LHC}, series = {Journal of High Energy Physics}, volume = {12}, journal = {Journal of High Energy Physics}, number = {86}, organization = {ATLAS Collaboration}, doi = {10.1007/JHEP12(2012)086}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-128133}, year = {2012}, abstract = {A search is conducted for hadronic three-body decays of a new massive coloured particle in √s=7TeV pp collisions at the LHC using an integrated luminosity of 4.6 fb\(^{-1}\) collected by the ATLAS detector. Supersymmetric gluino pair production in the context of a model with R-parity violation is used as a benchmark scenario. The analysis is divided into two search channels, each optimised separately for their sensitivity to high-mass and low-mass gluino production. The first search channel uses a stringent selection on the transverse momentum of the six leading jets and is performed as a counting experiment. The second search channel focuses on low-mass gluinos produced with a large boost. Large-radius jets are selected and the invariant mass of each of the two leading jets is used as a discriminant between the signal and the background. The results are found to be consistent with Standard Model expectations and limits are set on the allowed gluino mass.}, language = {en} } @article{OPUS4-12812, title = {Time-dependent angular analysis of the decay B\(^0_s\)→J/ψϕ and extraction of ΔΓ\(_s\) and the CP-violating weak phase ϕ\(_s\) by ATLAS}, series = {Journal of High Energy Physics}, volume = {12}, journal = {Journal of High Energy Physics}, number = {072}, organization = {ATLAS Collaboration}, doi = {10.1007/JHEP12(2012)072}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-128125}, year = {2012}, abstract = {A measurement of B\(^0_s\)→J/ψϕ decay parameters, including the CP -violating weak phase ϕ\(_s\) and the decay width difference ΔΓ\(_s\) is reported, using 4.9 fb\(^{-1}\) of integrated luminosity collected in 2011 by the ATLAS detector from LHC pp collisions at a centre-of-mass energy √s=7 TeV. The mean decay width Γ\(_s\) and the transversity amplitudes |A\(_0\)(0)|\(^2\) and |A\(_∥\)(0)|\(^2\) are also measured. The values reported for these parameters are: ϕ\(_s\)=0.22±0.41 (stat.)±0.10 (syst.) rad ΔΓ\(_s\)=0.053±0.021 (stat.)±0.010 (syst.)ps\(^{-1}\) Γ\(_s\)=0.677±0.007 (stat.)±0.004 (syst.) ps\(^{-1}\) |A\(_0\)(0)|\(^2\)=0.528±0.006 (stat.)±0.009 (syst.) |A\(_∥\)(0)|\(^2\)=0.220±0.008 (stat.)±0.007 (syst.) where the values quoted for ϕ\(_s\) and ΔΓ\(_s\) correspond to the solution compatible with the external measurements to which the strong phase δ\(_⊥\) is constrained and where ΔΓ\(_s\) is constrained to be positive. The fraction of S-wave KK or f\(_0\) contamination through the decays B\(^0_s\)→J/ψK\(^+\)K\(^-\)(f\(_0\)) is measured as well and is found to be consistent with zero. Results for ϕ\(_s\) and ΔΓ\(_s\) are also presented as 68\%, 90\% and 95\% likelihood contours, which show agreement with Standard Model expectations.}, language = {en} } @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{OPUS4-12798, title = {Search for anomalous production of prompt like-sign lepton pairs at √s=7TeV with the ATLAS detector}, series = {Journal of High Energy Physics}, volume = {12}, journal = {Journal of High Energy Physics}, number = {7}, organization = {ATLAS Collaboration}, doi = {10.1007/JHEP12(2012)007}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-127983}, year = {2012}, abstract = {An inclusive search for anomalous production of two prompt, isolated leptons with the same electric charge is presented. The search is performed in a data sample corresponding to 4.7 fb\(^{-1}\) of integrated luminosity collected in 2011 at √s=7TeV with the ATLAS detector at the LHC. Pairs of leptons (e\(^{±}\)e\(^{±}\), e\(^{±}\)μ\(^{±}\), and μ\(^{±}\)μ\(^{±}\)) with large transverse momentum are selected, and the dilepton invariant mass distribution is examined for any deviation from the Standard Model expectation. No excess is found, and upper limits on the production cross section of like-sign lepton pairs from physics processes beyond the Standard Model are placed as a function of the dilepton invariant mass within a fiducial region close to the experimental selection criteria. The 95\% confidence level upper limits on the cross section of anomalous e\(^{±}\)e\(^{±}\), e\(^{±}\)μ\(^{±}\), or μ\(^{±}\)μ\(^{±}\) production range between 1.7 fb and 64 fb depending on the dilepton mass and flavour combination.}, language = {en} } @article{OPUS4-12797, title = {Search for high-mass resonances decaying to dilepton final states in pp collisions at √s=7 TeV with the ATLAS detector}, series = {Journal of High Energy Physics}, volume = {11}, journal = {Journal of High Energy Physics}, number = {138}, organization = {ATLAS Collaboration}, doi = {10.1007/JHEP11(2012)138}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-127974}, year = {2012}, abstract = {The ATLAS detector at the Large Hadron Collider is used to search for high-mass resonances decaying to an electron-positron pair or a muon-antimuon pair. The search is sensitive to heavy neutral Z′ gauge bosons, Randall-Sundrum gravitons, Z* bosons, techni-mesons, Kaluza-Klein Z/γ bosons, and bosons predicted by Torsion models. Results are presented based on an analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 4.9 fb\(^{-1}\) in the e\(^+\)e\(^-\) channel and 5.0 fb\(^{-1}\) in the μ\(^+\)μ\(^-\)channel. A Z′ boson with Standard Model-like couplings is excluded at 95 \% confidence level for masses below 2.22 TeV. A Randall-Sundrum graviton with coupling k/\(\overline M_{Pl}\)=0.1 is excluded at 95 \% confidence level for masses below 2.16 TeV. Limits on the other models are also presented, including Technicolor and Minimal Z′ Models.}, language = {en} } @article{OPUS4-12796, title = {Measurement of W\(^{±}\)Z production in proton-proton collisions at √s=7 TeV with the ATLAS detector}, series = {European Physical Journal C}, volume = {72}, journal = {European Physical Journal C}, number = {2173}, organization = {ATLAS Collaboration}, doi = {10.1140/epjc/s10052-012-2173-0}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-127963}, year = {2012}, abstract = {A study of W\(^{±}\)Z production in proton-proton collisions at √s=7 TeV is presented using data corresponding to an integrated luminosity of 4.6 fb\(^{-1}\) collected with the ATLAS detector at the Large Hadron Collider in 2011. In total, 317 candidates, with a background expectation of 68±10 events, are observed in double-leptonic decay final states with electrons, muons and missing transverse momentum. The total cross-section is determined to be σ\(^{tot}_{WZ}\)=19.0\(^{+1.4}_{-1.3}\)(stat.)±0.9(syst.)±0.4(lumi.) pb, consistent with the Standard Model expectation of 17.6\(^{+1.1}_{-1.0}\) pb. Limits on anomalous triple gauge boson couplings are derived using the transverse momentum spectrum of Z bosons in the selected events. The cross-section is also presented as a function of Z boson transverse momentum and diboson invariant mass.}, language = {en} } @article{OPUS4-12795, title = {A search for \(t\overline t\) resonances with the ATLAS detector in 2.05 fb\(^{-1}\) of proton-proton collisions at √s=7 TeV}, series = {European Physical Journal C}, volume = {72}, journal = {European Physical Journal C}, number = {2083}, organization = {ATLAS Collaboration}, doi = {10.1140/epjc/s10052-012-2083-1}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-127959}, year = {2012}, abstract = {A search for top quark pair resonances in final states containing at least one electron or muon has been performed with the ATLAS experiment at the CERN Large Hadron Collider. The search uses a data sample corresponding to an integrated luminosity of 2.05 fb\(^{-1}\), which was recorded in 2011 at a proton-proton centre-of-mass energy of 7 TeV. No evidence for a resonance is found and limits are set on the production cross-section times branching ratio to \(t\overline t\) for narrow and wide resonances. For narrow Z′ bosons, the observed 95 \% Bayesian credibility level limits range from 9.3 pb to 0.95 pb for masses in the range of m Z′=500 GeV to m\(_{Z′}\)=1300 GeV. The corresponding excluded mass region for a leptophobic topcolour Z′ boson (Kaluza-Klein gluon excitation in the Randall-Sundrum model) is m\(_{Z′}\)<880 GeV (m\(_{gKK}\)<1130 GeV).}, language = {en} } @article{OPUS4-12781, title = {Measurement of event shapes at large momentum transfer with the ATLAS detector in pp collisions at √s=7 TeV}, series = {The European Physical Journal C}, volume = {72}, journal = {The European Physical Journal C}, number = {2211}, organization = {ATLAS Collaboration}, doi = {10.1140/epjc/s10052-012-2211-y}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-127813}, year = {2012}, abstract = {A measurement of event shape variables is presented for large momentum transfer proton-proton collisions using the ATLAS detector at the Large Hadron Collider. Six event shape variables calculated using hadronic jets are studied in inclusive multi-jet events in 35 pb\(^{-1}\) of integrated luminosity at a center-of-mass energy of √s=7 TeV. These measurements are compared to predictions by three Monte Carlo event generators containing leading-logarithmic parton showers matched to leading order matrix elements for 2→2 and 2→n (n=2,…,6) scattering. Measurements of the third-jet resolution parameter, aplanarity, thrust, sphericity, and transverse sphericity are generally well described. The mean value of each event shape variable is evaluated as a function of the average momentum of the two leading jets p\(_{T,1}\) and p\(_{T,2}\), with a mean p\(_T\) approaching 1 TeV.}, language = {en} } @article{OPUS4-12780, title = {Measurement of τ polarization in W→τν decays with the ATLAS detector in pp collisions at s√=7 TeV}, series = {The European Physical Journal C}, volume = {72}, journal = {The European Physical Journal C}, number = {2062}, organization = {ATLAS Collaboration}, doi = {10.1140/epjc/s10052-012-2062-6}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-127807}, year = {2012}, abstract = {In this paper, a measurement of τ polarization in W→τν decays is presented. It is measured from the energies of the decay products in hadronic τ decays with a single final state charged particle. The data, corresponding to an integrated luminosity of 24 pb\(^{-1}\), were collected by the ATLAS experiment at the Large Hadron Collider in 2010. The measured value of the τ polarization is P\(_τ\)=-1.06±0.04 (stat)\(^{+0.05}_{-0.07}\) (syst), in agreement with the Standard Model prediction, and is consistent with a physically allowed 95 \% CL interval [-1,-0.91]. Measurements of τ polarization have not previously been made at hadron colliders.}, language = {en} } @article{OPUS4-12785, title = {Search for anomaly-mediated supersymmetry breaking with the ATLAS detector based on a disappearing-track signature in pp collisions at √s=7 TeV}, series = {The European Physical Journal C}, volume = {72}, journal = {The European Physical Journal C}, number = {1993}, organization = {ATLAS Collaboration}, doi = {10.1140/epjc/s10052-012-1993-2}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-127850}, year = {2012}, abstract = {In models of anomaly-mediated supersymmetry breaking (AMSB), the lightest chargino is predicted to have a lifetime long enough to be detected in collider experiments. This letter explores AMSB scenarios in pp collisions at √s=7 TeV by attempting to identify decaying charginos which result in tracks that appear to have few associated hits in the outer region of the tracking system. The search was based on data corresponding to an integrated luminosity of 1.02 fb\(^{-1}\) collected with the ATLAS detector in 2011. The p\(_T\) spectrum of candidate tracks is found to be consistent with the expectation from Standard Model background processes and constraints on the lifetime and the production cross section were obtained. In the minimal AMSB framework with m\(_{3/2}\)<32 TeV, m\(_0\)<1.5 TeV, tanβ=5 and μ>0, a chargino having mass below 92 GeV and a lifetime between 0.5 ns and 2 ns is excluded at 95 \% confidence level.}, language = {en} } @article{OPUS4-12779, title = {Search for heavy neutrinos and right-handed W bosons in events with two leptons and jets in pp collisions at \(\sqrt{s}\)=7TeV with the ATLAS detector}, series = {The European Physical Journal C}, volume = {72}, journal = {The European Physical Journal C}, number = {2056}, organization = {The ATLAS Collaboration}, doi = {10.1140/epjc/s10052-012-2056-4}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-127796}, year = {2012}, abstract = {This letter reports on a search for hypothetical heavy neutrinos, N, and right-handed gauge bosons, W R, in events with high transverse momentum objects which include two reconstructed leptons and at least one hadronic jet. The results were obtained from data corresponding to an integrated luminosity of 2.1 fb\(^{-1}\) collected in proton-proton collisions at √s=7 TeV with the ATLAS detector at the CERN Large Hadron Collider. No excess above the Standard Model background expectation is observed. Excluded mass regions for Majorana and Dirac neutrinos are presented using two approaches for interactions that violate lepton and lepton-flavor numbers. One approach uses an effective operator framework, the other approach is guided by the Left-Right Symmetric Model. The results described in this letter represent the most stringent limits to date on the masses of heavy neutrinos and W\(_R\) bosons obtained in direct searches.}, language = {en} } @article{OPUS4-12763, title = {Search for lepton flavour violation in the eμ continuum with the ATLAS detector in √s=7 TeV pp collisions at the LHC}, series = {The European Physical Journal C}, volume = {72}, journal = {The European Physical Journal C}, number = {2040}, organization = {ATLAS Collaboration}, doi = {10.1140/epjc/s10052-012-2040-z}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-127632}, year = {2012}, abstract = {This paper presents a search for the t-channel exchange of an R-parity violating scalar top quark ( \(\tilde{t}\) ) in the e\(^±\) μ\(^∓\) continuum using 2.1 fb\(^{-1}\) of data collected by the ATLAS detector in √s=7 TeV pp collisions at the Large Hadron Collider. Data are found to be consistent with the expectation from the Standard Model backgrounds. Limits on R-parity-violating couplings at 95 \% C.L. are calculated as a function of the scalar top mass (m\(_\tilde{t}\)). The upper limits on the production cross section for pp→eμX, through the t-channel exchange of a scalar top quark, ranges from 170 fb for m\(_\tilde{t}\)=95 GeV to 30 fb for m\(_\tilde{t}\)=1000 GeV.}, 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 200MeV50 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{OPUS4-12753, title = {Performance of missing transverse momentum reconstruction in proton-proton collisions at √s=7 TeV with ATLAS}, series = {The European Physical Journal C}, volume = {72}, journal = {The European Physical Journal C}, number = {1844}, organization = {ATLAS Collaboration}, doi = {10.1140/epjc/s10052-011-1844-6}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-127530}, year = {2012}, abstract = {The measurement of missing transverse momentum in the ATLAS detector, described in this paper, makes use of the full event reconstruction and a calibration based on reconstructed physics objects. The performance of the missing transverse momentum reconstruction is evaluated using data collected in pp collisions at a centre-of-mass energy of 7 TeV in 2010. Minimum bias events and events with jets of hadrons are used from data samples corresponding to an integrated luminosity of about 0.3 nb\(^{-1}\) and 600 nb\(^{-1}\) respectively, together with events containing a Z boson decaying to two leptons (electrons or muons) or a W boson decaying to a lepton (electron or muon) and a neutrino, from a data sample corresponding to an integrated luminosity of about 36 pb\(^{-1}\). An estimate of the systematic uncertainty on the missing transverse momentum scale is presented}, language = {en} } @article{OPUS4-12752, title = {Search for top and bottom squarks from gluino pair production in final states with missing transverse energy and at least three b-jets with the ATLAS detector}, series = {The European Physical Journal C}, volume = {72}, journal = {The European Physical Journal C}, number = {2174}, organization = {The ATLAS Collaboration}, doi = {10.1140/epjc/s10052-012-2174-z}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-127523}, year = {2012}, abstract = {This letter reports the results of a search for top and bottom squarks from gluino pair production in 4.7 fb\(^{-1}\) of pp collisions at √s=7 TeV using the ATLAS detector at the LHC. The search is performed in events with large missing transverse momentum and at least three jets identified as originating from a b-quark. Exclusion limits are presented for a variety of gluino-mediated models with gluino masses up to 1 TeV excluded.}, language = {en} } @article{OPUS4-12751, title = {Search for a heavy top-quark partner in final states with two leptons with the ATLAS detector at the LHC}, series = {Journal of High Energy Physics}, volume = {11}, journal = {Journal of High Energy Physics}, number = {094}, organization = {ATLAS Collaboration}, doi = {10.1007/JHEP11(2012)094}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-127511}, year = {2012}, abstract = {The results of a search for direct pair production of heavy top-quark partners in 4.7 fb\(^{-1}\) of integrated luminosity from pp collisions at √s=7 TeV collected by the ATLAS detector at the LHC are reported. Heavy top-quark partners decaying into a top quark and a neutral non-interacting particle are searched for in events with two leptons in the final state. No excess above the Standard Model expectation is observed. Limits are placed on the mass of a supersymmetric scalar top and of a spin-1/2 top-quark partner. A spin-1/2 top-quark partner with a mass between 300 GeV and 480 GeV, decaying to a top quark and a neutral non-interacting particle lighter than 100 GeV, is excluded at 95\% confidence level.}, language = {en} } @article{OPUS4-12742, title = {Search for a fermiophobic Higgs boson in the diphoton decay channel with the ATLAS detector}, series = {The European Physical Journal C}, volume = {72}, journal = {The European Physical Journal C}, number = {2157}, organization = {ATLAS Collaboration}, doi = {10.1140/epjc/s10052-012-2157-0}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-127427}, year = {2012}, abstract = {A search for a fermiophobic Higgs boson using diphoton events produced in proton-proton collisions at a centre-of-mass energy of √s=7 TeV is performed using data corresponding to an integrated luminosity of 4.9 fb\(^{-1}\) collected by the ATLAS experiment at the Large Hadron Collider. A specific benchmark model is considered where all the fermion couplings to the Higgs boson are set to zero and the bosonic couplings are kept at the Standard Model values (fermiophobic Higgs model). The largest excess with respect to the background-only hypothesis is found at 125.5 GeV, with a local significance of 2.9 standard deviations, which reduces to 1.6 standard deviations when taking into account the look-elsewhere effect. The data exclude the fermiophobic Higgs model in the ranges 110.0-118.0 GeV and 119.5-121.0 GeV at 95 \% confidence level.}, language = {en} } @article{OPUS4-12741, title = {Measurement of the W boson polarization in top quark decays with the ATLAS detector}, series = {Journal of High Energy Physics}, volume = {06}, journal = {Journal of High Energy Physics}, number = {88}, organization = {ATLAS Collaboration}, doi = {10.1007/JHEP06(2012)088}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-127417}, year = {2012}, abstract = {This paper presents measurements of the polarization of W bosons in top quark decays, derived from \(t\overline{t}\) events with missing transverse momentum, one charged lepton and at least four jets, or two charged leptons and at least two jets. Data from pp collisions at a centre-of-mass energy of 7 TeV were collected with the ATLAS experiment at the LHC and correspond to an integrated luminosity of 1.04 fb\(^{-1}\). The measured fractions of longitudinally, left- and right-handed polarization are F\(_0\) = 0.67 ± 0.07, F\(_L\) = 0.32 ± 0.04 and F\(_R\) = 0.01 ± 0.05, in agreement with the Standard Model predictions. As the polarization of the W bosons in top quark decays is sensitive to the Wtb vertex Lorentz structure and couplings, the measurements were used to set limits on anomalous contributions to the Wtb couplings.}, language = {en} } @article{OPUS4-12735, title = {Measurement of inclusive two-particle angular correlations in pp collisions with the ATLAS detector at the LHC}, series = {Journal of High Energy Physics}, volume = {05}, journal = {Journal of High Energy Physics}, number = {157}, organization = {ATLAS Collaboration}, doi = {10.1007/JHEP05(2012)157}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-127350}, year = {2012}, abstract = {We present a measurement of two-particle angular correlations in proton- proton collisions at √s=900 GeV and 7 TeV. The collision events were collected during 2009 and 2010 with the ATLAS detector at the Large Hadron Collider using a single-arm minimum bias trigger. Correlations are measured for charged particles produced in the kinematic range of transverse momentum p\(_T\)  > 100 MeV and pseudorapidity |η| < 2.5. A complex structure in pseudorapidity and azimuth is observed at both collision energies. Results are compared to PYTHIA 8 and HERWIG++ as well as to the AMBT2B, DW and Perugia 2011 tunes of PYTHIA 6. The data are not satisfactorily described by any of these models.}, language = {en} } @article{AadAbbottAbdallahetal.2012, author = {Aad, G. and Abbott, B. and Abdallah, J. and Abdelalim, A. A. and Abdesselam, A.}, title = {Forward-backward correlations and charged-particle azimuthal distributions in pp interactions using the ATLAS detector}, series = {Journal of High Energy Physics}, volume = {7}, journal = {Journal of High Energy Physics}, number = {19}, organization = {ATLAS Collaboration}, doi = {10.1007/JHEP07(2012)019}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-127336}, year = {2012}, abstract = {Using inelastic proton-proton interactions at s√=900 GeV and 7 TeV, recorded by the ATLAS detector at the LHC, measurements have been made of the correlations between forward and backward charged-particle multiplicities and, for the first time, between forward and backward charged-particle summed transverse momentum. In addition, jet-like structure in the events is studied by means of azimuthal distributions of charged particles relative to the charged particle with highest transverse momentum in a selected kinematic region of the event. The results are compared with predictions from tunes of the pythia and herwig++ Monte Carlo generators, which in most cases are found to provide a reasonable description of the data.}, language = {en} } @article{AadAbbottAbdallahetal.2012, author = {Aad, G. and Abbott, B. and Abdallah, J. and Abdelalim, A. A. and Abdesselam, A.}, title = {Performance of the ATLAS Trigger System in 2010}, series = {The European Physical Journal C}, volume = {72}, journal = {The European Physical Journal C}, number = {1849}, doi = {10.1140/epjc/s10052-011-1849-1}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-127321}, year = {2012}, abstract = {Proton-proton collisions at √s=7 TeV and heavy ion collisions at \(\sqrt{sNN}\)=2.76 TeV were produced by the LHC and recorded using the ATLAS experiment's trigger system in 2010. The LHC is designed with a maximum bunch crossing rate of 40 MHz and the ATLAS trigger system is designed to record approximately 200 of these per second. The trigger system selects events by rapidly identifying signatures of muon, electron, photon, tau lepton, jet, and B meson candidates, as well as using global event signatures, such as missing transverse energy. An overview of the ATLAS trigger system, the evolution of the system during 2010 and the performance of the trigger system components and selections based on the 2010 collision data are shown. A brief outline of plans for the trigger system in 2011 is presented.}, language = {en} } @phdthesis{Hartmann2012, author = {Hartmann, Fabian}, title = {Elektrooptische Transporteigenschaften und stochastisch aktivierte Prozesse Resonanter Tunneldioden}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-90876}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2012}, abstract = {Im Rahmen der vorliegenden Arbeit wurden elektrooptische Transporteigenschaften und stochastisch aktivierte Prozesse Resonanter Tunneldioden (RTDs) bei Raumtemperatur untersucht. Die RTDs wurden auf dem III-V Halbleitermaterialsystem AlGaAs/GaAs durch Molekularstrahlepitaxie, Elektronenstrahllithographie und trockenchemischen {\"A}tztechniken hergestellt. Im Bereich des negativen differentiellen Leitwerts konnte bistabi-les Schalten und hierbei stochastisch aktivierte Dynamik nichtlinearer Systeme untersucht werden. Die Fl{\"a}chenabh{\"a}ngigkeit der {\"A}tzrate konnte ausgenutzt werden, um RTDs mit einem Stamm und zwei Transport{\"a}sten zu realisieren, welche hinsichtlich ihrer optischen und elektrischen Eigenschaften untersucht wurden. Im ersten experimentellen Abschnitt 3.1 werden die elektrischen Transporteigenschaften Resonanter Tunneldioden bei Raum-temperatur und die Fl{\"a}chenabh{\"a}ngigkeit des koh{\"a}renten und nicht-koh{\"a}renten Elektronen-transports analysiert. Die Realisierung universeller logischer Gatter (NOR und NAND) und deren Rekonfigurierbarkeit durch einen externen Kontrollparameter wird in Abschnitt 3.2 gezeigt. In Abschnitt 3.3 wird die Lichtsensitivit{\"a}t Resonanter Tunneldioden als Photode-tektoren f{\"u}r den sichtbaren Wellenl{\"a}ngenbereich und in Abschnitt 3.4 f{\"u}r die Telekommu-nikationswellenl{\"a}nge bei λ = 1,3 µm demonstriert.}, subject = {Resonanz-Tunneldiode}, language = {de} }