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Open Access Publications from the University of California

Scholarly Works (336 results)

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UC Santa Cruz Previously Published Works (2015)
    Cover page: Erratum to: Search for production of WW / WZ resonances decaying to a lepton, neutrino and jets in pp collisions at s=8 TeV with the ATLAS detectorCreative Commons 'BY' version 4.0 license
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    • Peer Reviewed
    UC Santa Cruz Previously Published Works (2014)
    ATLAS measurements of the azimuthal anisotropy in lead-lead collisions at [Formula: see text] TeV are shown using a dataset of approximately 7 [Formula: see text]b[Formula: see text] collected at the LHC in 2010. The measurements are performed for charged particles with transverse momenta [Formula: see text] GeV and in the pseudorapidity range [Formula: see text]. The anisotropy is characterized by the Fourier coefficients, [Formula: see text], of the charged-particle azimuthal angle distribution for [Formula: see text]-4. The Fourier coefficients are evaluated using multi-particle cumulants calculated with the generating function method. Results on the transverse momentum, pseudorapidity and centrality dependence of the [Formula: see text] coefficients are presented. The elliptic flow, [Formula: see text], is obtained from the two-, four-, six- and eight-particle cumulants while higher-order coefficients, [Formula: see text] and [Formula: see text], are determined with two- and four-particle cumulants. Flow harmonics [Formula: see text] measured with four-particle cumulants are significantly reduced compared to the measurement involving two-particle cumulants. A comparison to [Formula: see text] measurements obtained using different analysis methods and previously reported by the LHC experiments is also shown. Results of measurements of flow fluctuations evaluated with multi-particle cumulants are shown as a function of transverse momentum and the collision centrality. Models of the initial spatial geometry and its fluctuations fail to describe the flow fluctuations measurements.
      Cover page: Measurement of flow harmonics with multi-particle cumulants in Pb+Pb collisions at sNN=2.76 TeV with the ATLAS detectorCreative Commons 'BY' version 4.0 license
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      • Peer Reviewed
      UC Irvine Previously Published Works (2016)
      A measurement of the Bs0decay parameters in the Bs0→ J/ψϕ channel using an integrated luminosity of 14.3 fb−1collected by the ATLAS detector from 8 TeV pp collisions at the LHC is presented. The measured parameters include the CP -violating phase ϕs, the decay width Γs and the width difference between the mass eigenstates ΔΓs. The values measured for the physical parameters are statistically combined with those from 4.9 fb−1of 7 TeV data, leading to the following: Φs = -0.090 ± 0.078 (stat.) ± (syst.) rad Δ Γs = 0.085 ± 0.011 (stat.) ± 0.007 (syst.) Ps-1 Δ Γs = 0.675 ± 0.003 (stat.) ± 0.03 (syst.) Ps-1 In the analysis the parameter ΔΓs is constrained to be positive. Results for ϕs and ΔΓs are also presented as 68% and 95% likelihood contours in the ϕs-ΔΓs plane. Also measured in this decay channel are the transversity amplitudes and corresponding strong phases. All measurements are in agreement with the Standard Model predictions.[Figure not available: see fulltext.]
        Cover page: Measurement of the CP-violating phase ϕs and the Bs0 meson decay width difference with Bs0 → J/ψϕ decays in ATLASCreative Commons 'BY' version 4.0 license
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        • Peer Reviewed
        UC Irvine Previously Published Works (2018)
        A search for massive coloured resonances which are pair-produced and decay into two jets is presented. The analysis uses 36.7 fb - 1 of s = 13 TeV pp collision data recorded by the ATLAS experiment at the LHC in 2015 and 2016. No significant deviation from the background prediction is observed. Results are interpreted in a SUSY simplified model where the lightest supersymmetric particle is the top squark, t ~ , which decays promptly into two quarks through R-parity-violating couplings. Top squarks with masses in the range 100 GeV < m t ~ < 410   GeV are excluded at 95% confidence level. If the decay is into a b-quark and a light quark, a dedicated selection requiring two b-tags is used to exclude masses in the ranges 100 GeV < m t ~ < 470   GeV and 480 GeV < m t ~ < 610   GeV . Additional limits are set on the pair-production of massive colour-octet resonances.
          Cover page: A search for pair-produced resonances in four-jet final states at s=13TeV with the ATLAS detectorCreative Commons 'BY' version 4.0 license
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          • Peer Reviewed
          UC Santa Cruz Previously Published Works (2014)
          A search for an excess of events with multiple high transverse momentum objects including charged leptons and jets is presented, using 20.3 fb -1 of proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider in 2012 at a centre-of-mass energy of √s = 8 TeV. No excess of events beyond Standard Model expectations is observed. Using extra-dimensional models for black hole and string ball production and decay, exclusion contours are determined as a function of the mass threshold for production and the fundamental gravity scale for two, four and six extra dimensions. For six extra dimensions, mass thresholds of 4.8-6.2 TeV are excluded at 95 % confidence level, depending on the fundamental gravity scale and model assumptions. Upper limits on the fiducial cross-sections for non-Standard Model production of these final states are set. [Figure not available: see fulltext.] © 2014 The Author(s).
            Cover page: Search for microscopic black holes and string balls in final states with leptons and jets with the ATLAS detector at s = 8 TeVCreative Commons 'BY' version 4.0 license
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            UC Santa Cruz Previously Published Works (2020)
            Two additions impacting tables 3 and 4 in ref. [1] are presented in the following. No significant impact is found for other results or figures in ref. [1].
              Cover page: Erratum to: Measurement of differential cross sections and W+/W− cross-section ratios for W boson production in association with jets at s = 8 TeV with the ATLAS detector
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              • Peer Reviewed
              UC Santa Cruz Previously Published Works (2012)
              A measurement of the jet activity in [Formula: see text] 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 [Formula: see text] 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.
                Cover page: Measurement of production with a veto on additional central jet activity in pp collisions at TeV using the ATLAS detectorCreative Commons 'BY' version 4.0 license
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                • Peer Reviewed
                UC Irvine Previously Published Works (2013)
                Measurements of the production of jets of particles in association with a Z boson in pp collisions at √s=7 TeV are presented, using data corresponding to an integrated luminosity of 4.6 fb-1 collected by the ATLAS experiment at the Large Hadron Collider. Inclusive and differential jet cross sections in Z events, with Z decaying into electron or muon pairs, are measured for jets with transverse momentum p T > 30 GeV and rapidity |y| < 4.4. The results are compared to next-to-leading-order perturbative QCD calculations, and to predictions from different Monte Carlo generators based on leading-order and next-to-leading-order matrix elements supplemented by parton showers. [Figure not available: see fulltext.] © 2013 CERN for the benefit of the ATLAS collaboration.
                  Cover page: Measurement of the production cross section of jets in association with a Z boson in pp collisions at TeV with the ATLAS detectorCreative Commons 'BY' version 4.0 license
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                  • Peer Reviewed
                  UC Santa Cruz Previously Published Works (2012)
                  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 ΔηF, 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 < ΔηF < 8 for 200 MeV < pcutT < 800 MeV. At small ΔηF, the data test the reliability of hadronisation models in describing rapidity and transverse momentum fluctuations in final state particle production. The measurements at larger gap sizes are dominated by contributions from the single diffractive dissociation process (pp →Xp), enhanced by double dissociation (pp → XY) where the invariant mass of the lighter of the two dissociation systems satisfies MY < 7 GeV. The resulting cross section is dσ/dΔηF ≈1 mb for ΔηF > 3. The large rapidity gap data are used to constrain the value of the Pomeron intercept appropriate to triple Regge models of soft diffraction. The cross section integrated over all gap sizes is compared with other LHC inelastic cross section measurements.
                    Cover page: Rapidity gap cross sections measured with the ATLAS detector in pp collisions atCreative Commons 'BY' version 4.0 license
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                    • Peer Reviewed
                    UC Santa Cruz Previously Published Works (2012)
                    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. © 2012 Cern for the benefit of the ATLAS collaboration.
                      Cover page: Search for R-parity-violating supersymmetry in events with four or more leptons in \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$ \sqrt{s}=7\;\mathrm{TeV} $\end{document}pp collisions with the ATLAS detectorCreative Commons 'BY' version 4.0 license
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