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ATLAS measurements of the properties of jets for boosted particle searches

UC Santa Cruz Previously Published Works (2012)

Measurements are presented of the properties of high transverse momentum jets, produced in proton-proton collisions at a center-of-mass energy of √s=7TeV. The data correspond to an integrated luminosity of 35pb -1 and were collected with the ATLAS detector in 2010. Jet mass, width, eccentricity, planar flow and angularity are measured for jets reconstructed using the anti-kt algorithm with distance parameters R=0.6 and 1.0, with transverse momentum pT>300GeV and pseudorapidity |η|<2. The measurements are compared to the expectations of Monte Carlo generators that match leading-logarithmic parton showers to leading-order, or next-to-leading-order, matrix elements. The generators describe the general features of the jets, although discrepancies are observed in some distributions. © 2012 CERN, for the ATLAS Collaboration Published by the American Physical Society under the terms of the http://creativecommons. org/licenses/by/3.0/ Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Cover page: ATLAS measurements of the properties of jets for boosted particle searches

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Search for a standard model Higgs boson in the H→ZZ→ℓ+ℓ−νν¯ decay channel using 4.7 fb−1 of s=7 TeV data with the ATLAS detector

UC Berkeley Previously Published Works (2012)

A search for a Standard Model Higgs boson decaying via H→ZZ→ℓ+ℓ−νν¯ where ℓ represents electrons or muons, is presented. It is based on proton-proton collision data at s=7 TeV, collected by the ATLAS experiment at the LHC during 2011 and corresponding to an integrated luminosity of 4.7 fb−1. The data agree with the expected Standard Model backgrounds. Upper limits on the Higgs boson production cross section are derived for Higgs boson masses between 200 GeV and 600 GeV and the production of a Standard Model Higgs boson with a mass in the range 319–558 GeV is excluded at the 95% confidence level.

Cover page: Search for a standard model Higgs boson in the H→ZZ→ℓ+ℓ−νν¯ decay channel using 4.7 fb−1 of s=7 TeV data with the ATLAS detector

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Search for scalar top quark pair production in natural gauge mediated supersymmetry models with the ATLAS detector in pp collisions at s=7 TeV

UC Santa Cruz Previously Published Works (2012)

The results of a search for pair production of the lighter scalar partners of top quarks (t~1) in 2.05 fb -1 of pp collisions at s=7 TeV using the ATLAS experiment at the LHC are reported. Scalar top quarks are searched for in events with two same flavour opposite-sign leptons (e, μ) with invariant mass consistent with the Z boson mass, large missing transverse momentum and jets in the final state. At least one of the jets is identified as originating from a b-quark. No excess over Standard Model expectations is found. The results are interpreted in the framework of R-parity conserving, gauge mediated Supersymmetry breaking 'natural' scenarios, where the neutralino (χ~10) is the next-to-lightest supersymmetric particle. Scalar top quark masses up to 310 GeV are excluded for 115GeVmZ. © 2012 CERN.

Cover page: Search for scalar top quark pair production in natural gauge mediated supersymmetry models with the ATLAS detector in pp collisions at s=7 TeV

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Measurement of W±Z production in proton-proton collisions at with the ATLAS detector

UC Santa Cruz Previously Published Works (2012)

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 be σtotWZ = 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.

Cover page: Measurement of W±Z production in proton-proton collisions at with the ATLAS detector

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Search for light scalar top-quark pair production in final states with two leptons with the ATLAS detector in proton–proton collisions

UC Santa Cruz Previously Published Works (2012)

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.

Cover page: Search for light scalar top-quark pair production in final states with two leptons with the ATLAS detector in proton–proton collisions

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Search for the Higgs boson in the H→WW→ℓνjj decay channel at s=7 TeV with the ATLAS detector

UC Irvine Previously Published Works (2012)

A search for the Standard Model Higgs boson has been performed in the H→WW→ℓνjj channel using 4.7 fb−1 of pp collision data recorded at a centre-of-mass energy of s=7 TeV with the ATLAS detector at the Large Hadron Collider. Higgs boson candidates produced in association with zero, one or two jets are included in the analysis to maximize the acceptance for both gluon fusion and weak boson fusion Higgs boson production processes. No significant excess of events is observed over the expected background and limits on the Higgs boson production cross section are derived for a Higgs boson mass in the range 300 GeV

Cover page: Search for the Higgs boson in the H→WW→ℓνjj decay channel at s=7 TeV with the ATLAS detector

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Search for resonant top quark plus jet production in tt¯+jets events with the ATLAS detector in pp collisions at s=7 TeV

UC Santa Cruz Previously Published Works (2012)

This paper presents a search for a new heavy particle produced in association with a top or antitop quark. Two models in which the new heavy particle is a color singlet or a color triplet are considered, decaying, respectively, to t̄q or tq, leading to a resonance within the tt̄+jets signature. The full 2011 ATLAS pp collision data set from the LHC (4.7fb -1) is used to search for tt̄ events produced in association with jets, in which one of the W bosons from the top quarks decays leptonically and the other decays hadronically. The data are consistent with the Standard Model expectation, and a new particle with mass below 430 Gev for both W ′ boson and color triplet models is excluded at 95% confidence level, assuming unit right-handed coupling. © 2012 CERN.

Cover page: Search for resonant top quark plus jet production in tt¯+jets events with the ATLAS detector in pp collisions at s=7 TeV

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A search for resonances with the ATLAS detector in 2.05 fb−1 of proton-proton collisions at

UC Santa Cruz Previously Published Works (2012)

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 [Formula: see text] 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 ([Formula: see text]).

Cover page: A search for resonances with the ATLAS detector in 2.05 fb−1 of proton-proton collisions at

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Hunt for new phenomena using large jet multiplicities and missing transverse momentum with ATLAS in 4.7 fb−1 of proton-proton collisions

UC Santa Cruz Previously Published Works (2012)

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 = 7 TeV 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 m0, 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. Copyright CERN.

Cover page: Hunt for new phenomena using large jet multiplicities and missing transverse momentum with ATLAS in 4.7 fb−1 of proton-proton collisions

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Search for the decay Bs0→μ+μ− with the ATLAS detector

UC Santa Cruz Previously Published Works (2012)

A blind analysis searching for the decay Bs 0→μ+μ- has been performed using proton-proton collisions at a centre-of-mass energy of 7 TeV recorded with the ATLAS detector at the LHC. With an integrated luminosity of 2.4 fb-1 no excess of events over the background expectation is found and an upper limit is set on the branching fraction BR(Bs 0→μ+μ-)<2.2(1.9)×10-8 at 95% (90%) confidence level. © 2012 CERN.