@article{OPUS4-15008,
  title     = {Search for dark matter in events with heavy quarks and missing transverse momentum in pp collisions with the ATLAS detector},
  series = {European Physical Journal C: Particles and Fields},
  volume    = {75},
  journal   = {European Physical Journal C: Particles and Fields},
  number    = {2},
  organization    = {ATLAS Collaboration},
  doi       = {10.1140/epjc/s10052-015-3306-z},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-150089},
  pages     = {92},
  year      = {2015},
  abstract  = {This article reports on a search for dark matter pair production in association with bottom or top quarks in 20.3 fb\(^{-1}\) of pp collisions collected at \(\sqrt {s}\) = 8 TeV by the ATLAS detector at the LHC. Events with large missing transverse momentum are selected when produced in association with high-momentum jets of which one or more are identified as jets containing b-quarks. Final states with top quarks are selected by requiring a high jet multiplicity and in some cases a single lepton. The data are found to be consistent with the Standard Model expectations and limits are set on the mass scale of effective field theories that describe scalar and tensor interactions between dark matter and Standard Model particles. Limits on the dark-matter-nucleon cross-section for spin-independent and spin-dependent interactions are also provided. These limits are particularly strong for low-mass dark matter. Using a simplified model, constraints are set on the mass of dark matter and of a coloured mediator suitable to explain a possible signal of annihilating dark matter.},
  language  = {en}
}
@article{OPUS4-15011,
  title     = {Search for Higgs boson pair production in the b\(\overline{b}\)b\(\overline{b}\) final state from 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    = {9},
  organization    = {ATLAS Collaboration},
  doi       = {10.1140/epjc/s10052-015-3628-x},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-150119},
  pages     = {412},
  year      = {2015},
  abstract  = {A search for Higgs boson pair production pp → hh is performed with 19.5 fb\(^{-1}\) of proton-proton collision data at \(\sqrt {s}\) = 8 TeV, which were recorded by the ATLAS detector at the Large Hadron Collider in 2012. The decay products of each Higgs boson are reconstructed as a high-momentum b\(\overline{b}\) system with either a pair of small-radius jets or a single large-radius jet, the latter exploiting jet substructure techniques and associated b-tagged track-jets. No evidence for resonant or non-resonant Higgs boson pair production is observed. The data are interpreted in the context of the Randall-Sundrum model with a warped extra dimension as well as the two-Higgs-doublet model. An upper limit on the cross-section for pp → G\(^{*}_{KK}\) → hh → b\(\overline{b}\)b\(\overline{b}\) of 3.2(2.3) fb is set for a Kaluza-Klein graviton G\(^{*}_{KK}\) mass of 1.0(1.5) TeV, at the 95 \% confidence level. The search for non-resonant Standard Model hh production sets an observed 95 \% confidence level upper limit on the production cross-section σ(pp → hh → b\(\overline{b}\)b\(\overline{b}\)) of 202 fb, compared to a Standard Model prediction of σ(pp → hh → b\(\overline{b}\)b\(\overline{b}\)) = 3.6±0.5 fb.},
  language  = {en}
}
@article{OPUS4-15012,
  title     = {Search for invisible decays of the Higgs boson produced in association with a hadronically decaying vector boson in pp collisions at \(\sqrt {s}\) = TeV with the ATLAS detector},
  series = {European Physical Journal C: Particles and Fields},
  volume    = {75},
  journal   = {European Physical Journal C: Particles and Fields},
  number    = {7},
  organization    = {ATLAS Collaboration},
  doi       = {10.1140/epjc/s10052-015-3551-1},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-150126},
  pages     = {337},
  year      = {2015},
  abstract  = {A search for Higgs boson decays to invisible particles is performed using 20.3 fb\(^{-1}\) of pp collision data at a centre-of-mass energy of 8 TeV recorded by the ATLAS detector at the Large Hadron Collider. The process considered is Higgs boson production in association with a vector boson (V = W or Z) that decays hadronically, resulting in events with two or more jets and large missing transverse momentum. No excess of candidates is observed in the data over the background expectation. The results are used to constrain VH production followed by H decaying to invisible particles for the Higgs boson mass range 115 < m\(_{H}\) < 300 GeV. The 95 \% confidence-level observed upper limit on σ\(_{VH}\) × BR(H → inv.) varies from 1.6 pb at 115 GeV to 0.13 pb at 300 GeV. Assuming Standard Model production and including the gg → H contribution as signal, the results also lead to an observed upper limit of 78 \% at 95 \% confidence level on the branching ratio of Higgs bosons decays to invisible particles at a mass of 125 GeV.},
  language  = {en}
}
@article{OPUS4-15013,
  title     = {Search for invisible particles produced in association with single-top-quarks in proton-proton 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    = {2},
  organization    = {ATLAS Collaboration},
  doi       = {10.1140/epjc/s10052-014-3233-4},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-150134},
  pages     = {79},
  year      = {2015},
  abstract  = {A search for the production of single-top-quarks in association with missing energy is performed in proton-proton collisions at a centre-of-mass energy of \(\sqrt {s}\) =8 TeV with the ATLAS experiment at the large hadron collider using data collected in 2012, corresponding to an integrated luminosity of 20.3 fb\(^{-1}\). In this search, the W boson from the top quark is required to decay into an electron or a muon and a neutrino. No deviation from the standard model prediction is observed, and upper limits are set on the production cross-section for resonant and non-resonant production of an invisible exotic state in association with a right-handed top quark. In the case of resonant production, for a spin-0 resonance with a mass of 500 GeV, an effective coupling strength above 0.15 is excluded at 95 \% confidence level for the top quark and an invisible spin-1/2 state with mass between 0 and 100 GeV. In the case of non-resonant production, an effective coupling strength above 0.2 is excluded at 95 \% confidence level for the top quark and an invisible spin-1 state with mass between 0 and 657 GeV.},
  language  = {en}
}
@article{OPUS4-15014,
  title     = {Search for metastable heavy charged particles with large ionisation energy loss in pp collisions at \(\sqrt {s}\) = 8 TeV using the ATLAS experiment},
  series = {European Physical Journal C: Particles and Fields},
  volume    = {75},
  journal   = {European Physical Journal C: Particles and Fields},
  number    = {9},
  organization    = {ATLAS Collaboration},
  doi       = {10.1140/epjc/s10052-015-3609-0},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-150149},
  pages     = {407},
  year      = {2015},
  abstract  = {Many extensions of the Standard Model predict the existence of charged heavy long-lived particles, such as R-hadrons or charginos. These particles, if produced at the Large Hadron Collider, should be moving non-relativistically and are therefore identifiable through the measurement of an anomalously large specific energy loss in the ATLAS pixel detector. Measuring heavy long-lived particles through their track parameters in the vicinity of the interaction vertex provides sensitivity to metastable particles with lifetimes from 0.6 ns to 30 ns. A search for such particles with the ATLAS detector at the Large Hadron Collider is presented, based on a data sample corresponding to an integrated luminosity of 18.4 fb\(^{-1}\) of pp collisions at \(\sqrt {s}\) = 8 TeV. No significant deviation from the Standard Model background expectation is observed, and lifetime-dependent upper limits on R-hadrons and chargino production are set. Gluino R-hadrons with 10 ns lifetime and masses up to 1185 GeV are excluded at 95 \% confidence level, and so are charginos with 15 ns lifetime and masses up to 482 GeV.},
  language  = {en}
}
@article{OPUS4-15015,
  title     = {Search for new phenomena in final states with an energetic jet and large missing transverse momentum 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    = {7},
  organization    = {ATLAS Collaboration},
  doi       = {10.1140/epjc/s10052-015-3517-3},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-150152},
  pages     = {299},
  year      = {2015},
  abstract  = {Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb\(^{-1}\) of \(\sqrt {s}\) = 8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT > 120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between E\(^{miss}_{T}\) > 150 GeV and E\(^{miss}_{T}\) > 700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presented.},
  language  = {en}
}
@article{OPUS4-15017,
  title     = {Search for resonant diboson production in the ℓℓq\(\overline{q}\) final state 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    = {2},
  organization    = {ATLAS Collaboration},
  doi       = {10.1140/epjc/s10052-015-3261-8},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-150171},
  pages     = {69},
  year      = {2015},
  abstract  = {This paper reports on a search for narrow resonances in diboson production in the ℓℓq\(\overline{q}\) final state using pp collision data corresponding to an integrated luminosity of 20 fb\(^{-1}\) collected at \(\sqrt {s}\) = 8 TeV with the ATLAS detector at the Large Hadron Collider. No significant excess of data events over the Standard Model expectation is observed. Upper limits at the 95 \% confidence level are set on the production cross section times branching ratio for Kaluza-Klein gravitons predicted by the Randall-Sundrum model and for Extended Gauge Model W′ bosons. These results lead to the exclusion of mass values below 740 and 1590 GeV for the graviton and W′ boson respectively.},
  language  = {en}
}
@article{OPUS4-14997,
  title     = {Observation and measurements of the production of prompt and non-prompt J/ψ mesons in association with a Z boson 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/s10052-015-3406-9},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-149970},
  pages     = {229},
  year      = {2015},
  abstract  = {The production of a Z boson in association with a J/ψ meson in proton-proton collisions probes the production mechanisms of quarkonium and heavy flavour in association with vector bosons, and allows studies of multiple parton scattering. Using 20.3fb\(^{-1}\) of data collected with the ATLAS experiment at the LHC in pp collisions at \(\sqrt {s}\) = 8 TeV, the first measurement of associated Z+J/ψ production is presented for both prompt and non-prompt J/ψ production, with both signatures having a significance in excess of 5σ. The inclusive production cross-sections for Z boson production (analysed in μ\(^{+}\)μ\(^{-}\) or e\(^{+}\)e\(^{-}\) decay modes) in association with prompt and non-prompt J/ψ(→μ\(^{+}\)μ\(^{-}\)) are measured relative to the inclusive production rate of Z bosons in the same fiducial volume to be (36.8±6.7±2.5)×10\(^{-7}\) and (65.8±9.2±4.2)×10\(^{-7}\) respectively. Normalised differential production cross-section ratios are also determined as a function of the J/ψ transverse momentum. The fraction of signal events arising from single and double parton scattering is estimated, and a lower limit of 5.3 (3.7)mb at 68 (95)\% confidence level is placed on the effective cross-section regulating double parton interactions.},
  language  = {en}
}
@article{OPUS4-15006,
  title     = {Search for W' → tb → qqbb decays 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    = {4},
  organization    = {ATLAS Collaboration},
  doi       = {10.1140/epjc/s10052-015-3372-2},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-150068},
  pages     = {165},
  year      = {2015},
  abstract  = {A search for a massive W′ gauge boson decaying to a top quark and a bottom quark is performed with the ATLAS detector in pp collisions at the LHC. The dataset was taken at a centre-of-mass energy of \(\sqrt {s}\) = 8 TeV and corresponds to 20.3 fb\(^{-1}\) of integrated luminosity. This analysis is done in the hadronic decay mode of the top quark, where novel jet substructure techniques are used to identify jets from high-momentum top quarks. This allows for a search for high-mass W′ bosons in the range 1.5-3.0  TeV. b-tagging is used to identify jets originating from b-quarks. The data are consistent with Standard Model background-only expectations, and upper limits at 95 \% confidence level are set on the W′ → tb cross section times branching ratio ranging from 0.16 pb to 0.33 pb for left-handed W′ bosons, and ranging from 0.10 pb to 0.21 pb for W′ bosons with purely right-handed couplings. Upper limits at 95 \% confidence level are set on the W′-boson coupling to tb as a function of the W′ mass using an effective field theory approach, which is independent of details of particular models predicting a W′ boson.},
  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}
}