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Open Access Publications from the University of California

Scholarly Works (42 results)

  • Article
  • Peer Reviewed
UC San Diego Previously Published Works (2017)
The cross section of top quark-antiquark pair production in proton-proton collisions at [Formula: see text] is measured by the CMS experiment at the LHC, using data corresponding to an integrated luminosity of 2.2[Formula: see text]. The measurement is performed by analyzing events in which the final state includes one electron, one muon, and two or more jets, at least one of which is identified as originating from hadronization of a b quark. The measured cross section is [Formula: see text], in agreement with the expectation from the standard model.
    Cover page: Measurement of the tt¯ production cross section using events in the eμ final state in pp collisions at s=13TeV
    • Article
    • Peer Reviewed
    UC San Diego Previously Published Works (2014)
    Searches for the direct electroweak production of supersymmetric charginos, neutralinos, and sleptons in a variety of signatures with leptons and [Formula: see text], [Formula: see text], and Higgs bosons are presented. Results are based on a sample of proton-proton collision data collected at center-of-mass energy [Formula: see text] with the CMS detector in 2012, corresponding to an integrated luminosity of 19.5 [Formula: see text]. The observed event rates are in agreement with expectations from the standard model. These results probe charginos and neutralinos with masses up to 720 [Formula: see text], and sleptons up to 260 [Formula: see text], depending on the model details.
      Cover page: Searches for electroweak production of charginos, neutralinos, and sleptons decaying to leptons and W, Z, and Higgs bosons in pp collisions at 8 TeV
      • Article
      • Peer Reviewed
      UCLA Previously Published Works (2016)
      The differential cross section and charge asymmetry for inclusive [Formula: see text] production at [Formula: see text] are measured as a function of muon pseudorapidity. The data sample corresponds to an integrated luminosity of 18.8[Formula: see text] recorded with the CMS detector at the LHC. These results provide important constraints on the parton distribution functions of the proton in the range of the Bjorken scaling variable x from [Formula: see text] to [Formula: see text].
        Cover page: Measurement of the differential cross section and charge asymmetry for inclusive pp→W±+X production at s=8 TeV
        • Article
        • Peer Reviewed
        UCLA Previously Published Works (2016)
        A measurement of the W boson pair production cross section in proton-proton collisions at [Formula: see text] TeV is presented. The data collected with the CMS detector at the LHC correspond to an integrated luminosity of 19.4[Formula: see text]. The [Formula: see text] candidates are selected from events with two charged leptons, electrons or muons, and large missing transverse energy. The measured [Formula: see text] cross section is [Formula: see text], consistent with the standard model prediction. The [Formula: see text] cross sections are also measured in two different fiducial phase space regions. The normalized differential cross section is measured as a function of kinematic variables of the final-state charged leptons and compared with several perturbative QCD predictions. Limits on anomalous gauge couplings associated with dimension-six operators are also given in the framework of an effective field theory. The corresponding 95 % confidence level intervals are [Formula: see text], [Formula: see text], [Formula: see text], in the HISZ basis.
          Cover page: Measurement of the W+W- cross section in pp collisions at s=8 TeVand limits on anomalous gauge couplings
          • Article
          • Peer Reviewed
          UC Riverside Previously Published Works (2015)
          Properties of the Higgs boson with mass near 125[Formula: see text] are measured in proton-proton collisions with the CMS experiment at the LHC. Comprehensive sets of production and decay measurements are combined. The decay channels include [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] pairs. The data samples were collected in 2011 and 2012 and correspond to integrated luminosities of up to 5.1[Formula: see text] at 7[Formula: see text] and up to 19.7[Formula: see text] at 8[Formula: see text]. From the high-resolution [Formula: see text] and [Formula: see text] channels, the mass of the Higgs boson is determined to be [Formula: see text]. For this mass value, the event yields obtained in the different analyses tagging specific decay channels and production mechanisms are consistent with those expected for the standard model Higgs boson. The combined best-fit signal relative to the standard model expectation is [Formula: see text] at the measured mass. The couplings of the Higgs boson are probed for deviations in magnitude from the standard model predictions in multiple ways, including searches for invisible and undetected decays. No significant deviations are found.
            Cover page: Precise determination of the mass of the Higgs boson and tests of compatibility of its couplings with the standard model predictions using proton collisions at 7 and 8TeV
            • Article
            • Peer Reviewed
            UCLA Previously Published Works (2017)
            A search for new phenomena is performed in final states containing one or more jets and an imbalance in transverse momentum in pp collisions at a centre-of-mass energy of 13[Formula: see text]. The analysed data sample, recorded with the CMS detector at the CERN LHC, corresponds to an integrated luminosity of 2.3[Formula: see text]. Several kinematic variables are employed to suppress the dominant background, multijet production, as well as to discriminate between other standard model and new physics processes. The search provides sensitivity to a broad range of new-physics models that yield a stable weakly interacting massive particle. The number of observed candidate events is found to agree with the expected contributions from standard model processes, and the result is interpreted in the mass parameter space of fourteen simplified supersymmetric models that assume the pair production of gluinos or squarks and a range of decay modes. For models that assume gluino pair production, masses up to 1575 and 975[Formula: see text] are excluded for gluinos and neutralinos, respectively. For models involving the pair production of top squarks and compressed mass spectra, top squark masses up to 400[Formula: see text] are excluded.
              Cover page: A search for new phenomena in pp collisions at s=13TeV in final states with missing transverse momentum and at least one jet using the αT variable
              • Article
              • Peer Reviewed
              UCLA Previously Published Works (2016)
              A measurement of the forward-backward asymmetry [Formula: see text] of oppositely charged lepton pairs ([Formula: see text] and [Formula: see text]) produced via [Formula: see text] boson exchange in pp collisions at [Formula: see text] [Formula: see text] is presented. The data sample corresponds to an integrated luminosity of 19.7[Formula: see text] collected with the CMS detector at the LHC. The measurement of [Formula: see text] is performed for dilepton masses between 40[Formula: see text] and 2[Formula: see text] and for dilepton rapidity up to 5. The [Formula: see text] measurements as a function of dilepton mass and rapidity are compared with the standard model predictions.
                Cover page: Forward–backward asymmetry of Drell–Yan lepton pairs in pp collisions at s=8TeV
                • Article
                • Peer Reviewed
                UCLA Previously Published Works (2017)
                The nuclear modification factor [Formula: see text] and the azimuthal anisotropy coefficient [Formula: see text] of prompt and nonprompt (i.e. those from decays of b hadrons) [Formula: see text] mesons, measured from PbPb and pp collisions at [Formula: see text] [Formula: see text] at the LHC, are reported. The results are presented in several event centrality intervals and several kinematic regions, for transverse momenta [Formula: see text] [Formula: see text] and rapidity [Formula: see text], extending down to [Formula: see text] [Formula: see text] in the [Formula: see text] range. The [Formula: see text] of prompt [Formula: see text] is found to be nonzero, but with no strong dependence on centrality, rapidity, or [Formula: see text] over the full kinematic range studied. The measured [Formula: see text] of nonprompt [Formula: see text] is consistent with zero. The [Formula: see text] of prompt [Formula: see text] exhibits a suppression that increases from peripheral to central collisions but does not vary strongly as a function of either y or [Formula: see text] in the fiducial range. The nonprompt [Formula: see text] [Formula: see text] shows a suppression which becomes stronger as rapidity or [Formula: see text] increases. The [Formula: see text] and [Formula: see text] of open and hidden charm, and of open charm and beauty, are compared.
                  Cover page: Suppression and azimuthal anisotropy of prompt and nonprompt J/ψ production in PbPb collisions at sNN=2.76TeV
                  • Article
                  • Peer Reviewed
                  UC Riverside Previously Published Works (2015)
                  A search for a standard model Higgs boson produced in association with a top-quark pair and decaying to bottom quarks is presented. Events with hadronic jets and one or two oppositely charged leptons are selected from a data sample corresponding to an integrated luminosity of 19.5[Formula: see text] collected by the CMS experiment at the LHC in [Formula: see text] collisions at a centre-of-mass energy of 8[Formula: see text]. In order to separate the signal from the larger [Formula: see text]  + jets background, this analysis uses a matrix element method that assigns a probability density value to each reconstructed event under signal or background hypotheses. The ratio between the two values is used in a maximum likelihood fit to extract the signal yield. The results are presented in terms of the measured signal strength modifier, [Formula: see text], relative to the standard model prediction for a Higgs boson mass of 125[Formula: see text]. The observed (expected) exclusion limit at a 95 % confidence level is [Formula: see text] (3.3), corresponding to a best fit value [Formula: see text].
                    Cover page: Search for a standard model Higgs boson produced in association with a top-quark pair and decaying to bottom quarks using a matrix element method
                    • Article
                    • Peer Reviewed
                    UC San Diego Previously Published Works (2015)
                    This paper presents distributions of topological observables in inclusive three- and four-jet events produced in pp collisions at a centre-of-mass energy of 7[Formula: see text] with a data sample collected by the CMS experiment corresponding to a luminosity of 5.1[Formula: see text]. The distributions are corrected for detector effects, and compared with several event generators based on two- and multi-parton matrix elements at leading order. Among the considered calculations, MadGraph interfaced with pythia6 displays the overall best agreement with data.
                      Cover page: Distributions of topological observables in inclusive three- and four-jet events in pp collisions at [Formula: see text][Formula: see text].
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