Browsing by Subject "B physics"

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  • The CMS collaboration; Sirunyan, A. M.; Tumasyan, A.; Eerola, P.; Forthomme, Laurent; Kirschenmann, H.; Österberg, K.; Voutilainen, M.; Brücken, Erik; Garcia, F.; Havukainen, J.; Heikkilä, Jaana; Karimäki, V.; Kim, Minsuk; Kinnunen, R.; Kortelainen, Matti; Lampén, T.; Lassila-Perini, K.; Laurila, Santeri; Lehti, S.; Lindén, T.; Luukka, P.; Pekkanen, Juska; Siikonen, H.; Tuominen, E.; Tuominiemi, J.; Viinikainen, Jussi; Tuuva, T. (2021)
    Angular distributions of the decay B+-> K*(892)(+)mu(+)mu(-) are studied using events collected with the CMS detector in root 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.
  • The CMS collaboration; Sirunyan, A. M.; Tumasyan, A.; Eerola, P.; Forthomme, Laurent; Kirschenmann, H.; Österberg, K.; Voutilainen, M.; Brücken, Erik; Garcia, F.; Havukainen, J.; Heikkilä, J.K.; Karimäki, V.; Kim, Minsuk; Kinnunen, R.; Lampén, T.; Lassila-Perini, K.; Laurila, S.; Lehti, S.; Lindén, T.; Luukka, P.; Pekkanen, Juska; Siikonen, H.; Tuominen, E.; Tuominiemi, J.; Viinikainen, Jussi; Tuuva, T. (2021)
    We present the first study of charged-hadron production associated with jets originating from b quarks in proton-proton collisions at a center-of-mass energy of 5.02 TeV. The data sample used in this study was collected with the CMS detector at the CERN LHC and corresponds to an integrated luminosity of 27.4 pb(-1). To characterize the jet substructure, the differential jet shapes, defined as the normalized transverse momentum distribution of charged hadrons as a function of angular distance from the jet axis, are measured for b jets. In addition to the jet shapes, the per-jet yields of charged particles associated with b jets are also quantified, again as a function of the angular distance with respect to the jet axis. Extracted jet shape and particle yield distributions for b jets are compared with results for inclusive jets, as well as with the predictions from the pythia and herwig++ event generators.
  • The CMS collaboration; Tumasyan, A.; Adam, W.; Eerola, P.; Forthomme, Laurent; Kirschenmann, H.; Österberg, K.; Voutilainen, M.; Brücken, Erik; Garcia, F.; Havukainen, J.; Heikkilä, Jaana; Karimäki, Veikko; Kim, Minsuk; Kinnunen, R.; Lampén, T.; Lassila-Perini, K.; Laurila, S.; Lehti, S.; Lindén, T.; Luukka, P.; Pekkanen, Juska; Siikonen, H.; Tuominen, E.; Tuominiemi, J.; Viinikainen, Jussi; Tuuva, T. (2021)
    The production cross sections for prompt open-charm mesons in proton-proton collisions at a center-of-mass energy of 13TeV are reported. The measurement is performed using a data sample collected by the CMS experiment corresponding to an integrated luminosity of 29 nb(-1). The differential production cross sections of the D*(+/-), D-+/-, and D-0 ((D) over bar (0)) mesons are presented in ranges of transverse momentum and pseudorapidity 4 < p(T) < 100 GeV and vertical bar eta vertical bar < 2.1, respectively. The results are compared to several theoretical calculations and to previous measurements.
  • The CMS collaboration; Sirunyan, A. M.; Eerola, P.; Forthomme, L.; Kirschenmann, H.; Österberg, K.; Voutilainen, M.; Garcia, F.; Havukainen, J.; Heikkilä, J. K.; Karimäki, V.; Kim, M. S.; Kinnunen, R.; Lampen, T.; Lassila-Perini, K.; Laurila, S.; Lehti, S.; Linden, T.; Luukka, P.; Mäenpää, T.; Siikonen, H.; Tuominen, E.; Tuominiemi, J.; Tuuva, T.; Viinikainen, J.; Pekkanen, J.; Tumasyan, A. (2020)
    Results are reported for the B 0s ! + branching fraction and effective lifetime and from a search for the decay B0 ! + . The analysis uses a data sample of proton-proton collisions accumulated by the CMS experiment in 2011, 2012, and 2016, with center-of-mass energies (integrated luminosities) of 7TeV (5 fb), 8TeV (20 fb), and 13TeV (36 fb). The branching fractions are determined by measuring event yields relative to B+ ! J= K+ decays (with J= ! + ), which results in the reduction of many of the systematic uncertainties. The decay B 0s ! + is observed with a significance of 5.6 standard deviations. The branching fraction is measured to be B (B 0s ! + ) = [2:9 0:7(exp) 0:2(frag)] 10, where the first uncertainty combines the experimental statistical and systematic contributions, and the second is due to the uncertainty in the ratio of the B 0s and the B+ fragmentation functions. No significant excess is observed for the decay B0 ! + , and an upper limit of B(B0 ! + ) <3:6 10 is obtained at 95% confidence level. The B 0s ! + effective lifetime is measured to be + = 1:70 +0:61 ps. These results are consistent with standard model predictions.
  • The CMS collaboration; Sirunyan, A. M.; Tumasyan, A.; Eerola, P.; Forthomme, Laurent; Kirschenmann, H.; Österberg, K.; Voutilainen, M.; Brücken, Erik; Garcia, F.; Havukainen, J.; Karimäki, V.; Kim, Minsuk; Kinnunen, R.; Lampén, T.; Lassila-Perini, K.; Laurila, S.; Lehti, S.; Lindén, T.; Luukka, P.; Pekkanen, Juska; Siikonen, H.; Tuominen, E.; Tuominiemi, J.; Viinikainen, Jussi; Tuuva, T. (2021)
    The CP-violating weak phase ?s and the decay width difference ??s between the light and heavy B0s mass eigenstates are measured with the CMS detector at the LHC in a sample of 48 500 reconstructed B0s? J/I) d (1020) ?11+11? K+K? events. The measurement is based on a data sample corresponding to an integrated luminosity of 96.4 fb?1, collected in proton-proton collisions at ?s = 13 TeV in 2017?2018. To extract the values of ?s and ??s, a time-dependent and flavor-tagged angular analysis of the 11+11?K+K? final state is performed. The analysis employs a dedicated tagging trigger and a novel opposite-side muon flavor tagger based on machine learning techniques. The measurement yields ?s = ?11 ?50 (stat) ? 10 (syst) mrad and ??s = 0.114 ? 0.014 (stat)? 0.007 (syst) ps?1, in agreement with the standard model predictions. When combined with the previous CMS measurement at ?s = 8 TeV, the following values are obtained: ?s = ?21 ? 44 (stat) ? 10 (syst) mrad, ??s = 0.1032 ? 0.0095 (stat) ? 0.0048 (syst) ps?1, a significant improvement over the 8 TeV result. ? 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license
  • The CMS collaboration; Sirunyan, A. M.; Eerola, P.; Forthomme, L.; Kirschenmann, H.; Osterberg, K.; Voutilainen, M.; Garcia, F.; Havukainen, J.; Heikkila, J. K.; Jarvinen, T.; Kinnunen, R.; Lampen, T.; Lassila-Perini, K.; Laurila, S.; Lehti, S.; Linden, T.; Luukka, P.; Maenpaa, T.; Siikonen, H.; Tuominen, E.; Tuominiemi, J.; Tuuva, Tuure (2019)
    A study of the B+-> J/psi = 8 TeV by the CMS experiment at the LHC, corresponding to an integrated luminosity of 19.6 fb(-1), is presented. The ratio of branching fractions B+-> J/psi B+-> J/psi K is measured to be (1.054 +/- 0.057(stat) +/- 0.035(syst) +/- 0.011 where the last uncertainty reflects the uncertainties in the world-average branching fractions of and K*(892) (+) decays to reconstructed final states. The invariant mass distributions of the J/psi, J/psi systems produced in the B+-> J/psi decay are investigated and found to be inconsistent with the pure phase space hypothesis. The analysis is extended by using a model-independent angular amplitude analysis, which shows that the observed invariant mass distributions are consistent with the contributions from excited kaons decaying to the (Lambda) over barp system.