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  • Open Access

Measurement of the Bc− meson production fraction and asymmetry in 7 and 13 TeV pp collisions

R. Aaij et al. (LHCb Collaboration)
Phys. Rev. D 100, 112006 – Published 13 December 2019
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  • INTRODUCTION
  • DETECTOR, TRIGGER, AND SIMULATION
  • EVENT SELECTION, SIGNAL EFFICIENCIES AND…
  • RESULTS
  • SYSTEMATIC UNCERTAINTIES
  • CONCLUSIONS
  • ACKNOWLEDGMENTS
    • References

    Abstract

    The production fraction of the Bc− meson with respect to the sum of B− and B¯0 mesons is measured in both 7 and 13 TeV center-of-mass (c.m.) energy pp collisions produced by the Large Hadron Collider (LHC), using the LHCb detector. The rate, approximately 3.7 per mille, does not change with energy, but shows a transverse momentum dependence. The Bc−−Bc+ production asymmetry is also measured and is consistent with zero within the determined statistical and systematic uncertainties of a few percent.

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    • Received 30 October 2019

    DOI:https://doi.org/10.1103/PhysRevD.100.112006

    Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.

    © 2019 CERN, for the LHCb Collaboration

    Physics Subject Headings (PhySH)

    1. Research Areas
    Particle interactionsParticle productionQuantum chromodynamicsStrong interaction
    Particles & Fields

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    Issue

    Vol. 100, Iss. 11 — 1 December 2019

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    • Figure 1
      Figure 1

      Distributions of corrected mass mcor and m(J/ψμ−) for (top) 7 TeV and (bottom) 13 TeV data, where (a) and (c) are data and (b) and (d) simulated signal. The (red) dashed line indicates the m(J/ψμ−)>4.5  GeV requirement.

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    • Figure 2
      Figure 2

      Fitted mcor distributions in (a) 7 TeV and (b) 13 TeV samples. The signal and the backgrounds are shown as the dark (orange) and lighter (gray) areas. The dashed (cyan) curves show the Bc−→J/ψτ−ντ components, while the dotted (blue) curves show the Bc−→χc0,1,2μ−ν¯ components. The Bc−→ψ(2S)μ−ν¯ contribution is also in the fit but is too small to be seen. The total fit is shown by the solid (red) curve.

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    • Figure 3
      Figure 3

      The total efficiency for Bc−→J/ψμ−ν¯, as a function of pT(Bc−) in different intervals of η in (a) 7 TeV and (b) 13 TeV samples.

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    • Figure 4
      Figure 4

      Invariant-mass distributions of (a) K−π+ and (b) K−π+π+ for 7 TeV, and (c) and (d) for 13 TeV collisions. The data are shown by solid points. The (red) dashed lines represent the signal components. The combinatorial backgrounds are shown as the dotted (magenta) line, and the solid (blue) line shows the total fit.

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    • Figure 5
      Figure 5

      Total efficiencies for the (a) D0Xμ−ν¯ and (b) D+Xμ−ν¯ signals in 7 TeV and (c) and (d) 13 TeV samples as functions of pT in η intervals.

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    • Figure 6
      Figure 6

      The k-factor corrections as a function of invariant mass of (a) m(J/ψμ−), (b) m(D0μ−), and (c) m(D+μ−) for the 13 TeV simulation samples. (The 7 TeV results are almost identical.) The points (magenta) are the average k-factor corrections, and the (green) dashed line shows a second-order polynomial fit to the average data.

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    • Figure 7
      Figure 7

      Ratio of production fractions after the k-factor correction as a function of (a) pT(Hb) and (c) η in 7 TeV data and (b) and (d) in 13 TeV data. The smaller error bars show the statistical uncertainties, and the larger ones include the statistical and systematic uncertainties. The horizontal (green) dashed-lines show the average values.

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    • Figure 8
      Figure 8

      Ratio of the Bc− production fractions at 13–7 TeV as a function of (a) pT(Hb) and (b) η. The smaller error bars show the statistical uncertainties, and the larger ones include the statistical and systematic uncertainties added in quadrature.

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