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Open Access Publications from the University of California

Scholarly Works (35 results)

  • Article
  • Peer Reviewed
UC San Diego Previously Published Works (2021)
Measurements are presented of differential cross sections for the production of Z bosons in association with at least one jet initiated by a charm quark in pp collisions at s = 13 TeV. The data recorded by the CMS experiment at the LHC correspond to an integrated luminosity of 35.9 fb−1. The final states contain a pair of electrons or muons that are the decay products of a Z boson, and a jet consistent with being initiated by a charm quark produced in the hard interaction. Differential cross sections as a function of the transverse momentum pT of the Z boson and pT of the charm jet are compared with predictions from Monte Carlo event generators. The inclusive production cross section 405.4 ± 5.6 (stat) ± 24.3 (exp) ± 3.7 (theo) pb, is measured in a fiducial region requiring both leptons to have pseudorapidity |η| < 2.4 and pT> 10 GeV, at least one lepton with pT> 26 GeV, and a mass of the pair in the range 71–111 GeV, while the charm jet is required to have pT> 30 GeV and |η| < 2.4. These are the first measurements of these cross sections in proton-proton collisions at 13 TeV. [Figure not available: see fulltext.]
    Cover page: Measurement of differential cross sections for Z bosons produced in association with charm jets in pp collisions at √s = 13 TeV
    • Article
    • Peer Reviewed
    LBL Publications (2023)
    The production of Z bosons associated with jets is measured in pp collisions at s=13TeV with data recorded with the CMS experiment at the LHC corresponding to an integrated luminosity of 36.3fb-1. The multiplicity of jets with transverse momentum pT>30GeV is measured for different regions of the Z bosons pT(Z), from lower than 10GeV to higher than 100GeV. The azimuthal correlation Δϕ between the Z boson and the leading jet, as well as the correlations between the two leading jets are measured in three regions of pT(Z). The measurements are compared with several predictions at leading and next-to-leading orders, interfaced with parton showers. Predictions based on transverse-momentum dependent parton distributions and corresponding parton showers give a good description of the measurement in the regions where multiple parton interactions and higher jet multiplicities are not important. The effects of multiple parton interactions are shown to be important to correctly describe the measured spectra in the low pT(Z) regions.
      Cover page: Azimuthal correlations in Z +jets events in proton-proton collisions at s=13TeV.
      • Article
      • Peer Reviewed
      LBL Publications (2023)
      Multijet events at large transverse momentum (pT) are measured at s=13TeV using data recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 36.3fb-1. The multiplicity of jets with pT>50GeV that are produced in association with a high-pT dijet system is measured in various ranges of the pT of the jet with the highest transverse momentum and as a function of the azimuthal angle difference Δϕ1,2 between the two highest pT jets in the dijet system. The differential production cross sections are measured as a function of the transverse momenta of the four highest pT jets. The measurements are compared with leading and next-to-leading order matrix element calculations supplemented with simulations of parton shower, hadronization, and multiparton interactions. In addition, the measurements are compared with next-to-leading order matrix element calculations combined with transverse-momentum dependent parton densities and transverse-momentum dependent parton shower.
        Cover page: Measurements of jet multiplicity and jet transverse momentum in multijet events in proton-proton collisions at s=13TeV.
        • Article
        • Peer Reviewed
        UC Riverside Previously Published Works (2021)
        Angular distributions of the decay B+→ K∗(892)+μ+μ− are studied using events collected with the CMS detector in s = 8 TeV proton-proton collisions at the LHC, corresponding to an integrated luminosity of 20.0 fb−1. The forward-backward asymmetry of the muons and the longitudinal polarization of the K∗(892)+ meson are determined as a function of the square of the dimuon invariant mass. These are the first results from this exclusive decay mode and are in agreement with a standard model prediction. [Figure not available: see fulltext.]
          Cover page: Angular analysis of the decay B+→ K∗(892)+μ+μ− in proton-proton collisions at s = 8 TeV
          • Article
          • Peer Reviewed
          UC San Diego Previously Published Works (2022)
          A search for new long-lived particles decaying to leptons using proton-proton collision data produced by the CERN LHC at s=13Te is presented. Events are selected with two leptons (an electron and a muon, two electrons, or two muons) that both have transverse impact parameter values between 0.01 and 10 cm and are not required to form a common vertex. Data used for the analysis were collected with the CMS detector in 2016, 2017, and 2018, and correspond to an integrated luminosity of 118 (113) fb-1 in the ee channel ( eμ and μμ channels). The search is designed to be sensitive to a wide range of models with displaced eμ , ee , and μμ final states. The results constrain several well-motivated models involving new long-lived particles that decay to displaced leptons. For some areas of the available phase space, these are the most stringent constraints to date.
            Cover page: Search for long-lived particles decaying to leptons with large impact parameter in proton–proton collisions at s=13Te
            • Article
            • Peer Reviewed
            UC Riverside Previously Published Works (2020)
            A measurement of the mass of the Higgs boson in the diphoton decay channel is presented. This analysis is based on 35.9fb−1 of proton-proton collision data collected during the 2016 LHC running period, with the CMS detector at a centre-of-mass energy of 13 TeV. A refined detector calibration and new analysis techniques have been used to improve the precision of this measurement. The Higgs boson mass is measured to be mH=125.78±0.26GeV. This is combined with a measurement of mH already performed in the H→ZZ→4ℓ decay channel using the same data set, giving mH=125.46±0.16GeV. This result, when further combined with an earlier measurement of mH using data collected in 2011 and 2012 with the CMS detector, gives a value for the Higgs boson mass of mH=125.38±0.14GeV. This is currently the most precise measurement of the mass of the Higgs boson.
              Cover page: A measurement of the Higgs boson mass in the diphoton decay channel
              • Article
              • Peer Reviewed
              UC San Diego Previously Published Works (2020)
              A search for new physics in events with two highly Lorentz-boosted Z bosons and large missing transverse momentum is presented. The analyzed proton-proton collision data, corresponding to an integrated luminosity of 137 fb−1, were recorded at s = 13 TeV by the CMS experiment at the CERN LHC. The search utilizes the substructure of jets with large radius to identify quark pairs from Z boson decays. Backgrounds from standard model processes are suppressed by requirements on the jet mass and the missing transverse momentum. No significant excess in the event yield is observed beyond the number of background events expected from the standard model. For a simplified supersymmetric model in which the Z bosons arise from the decay of gluinos, an exclusion limit of 1920 GeV on the gluino mass is set at 95% confidence level. This is the first search for beyond-standard-model production of pairs of boosted Z bosons plus large missing transverse momentum. [Figure not available: see fulltext.]
                Cover page: Search for supersymmetry in proton-proton collisions at s = 13 TeV in events with high-momentum Z bosons and missing transverse momentum
                • Article
                • Peer Reviewed