Measurement of properties of Bs0 → μ+μ decays and search for B0 → μ+μ with the CMS experiment

The CMS collaboration

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Results are reported for the Bs0→ μ+μ branching fraction and effective lifetime and from a search for the decay B0→ μ+μ. 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 7 TeV (5 fb−1), 8 TeV (20 fb−1), and 13 TeV (36 fb−1). The branching fractions are determined by measuring event yields relative to B+→ J/ψK+ decays (with J/ψ → μ+μ), which results in the reduction of many of the systematic uncertainties. The decay Bs0→ μ+μ is observed with a significance of 5.6 standard deviations. The branching fraction is measured to be ℬ(Bs0→μ+μ−)=[2.9±0.7(exp)±0.2(frag)]×10−9, where the first uncertainty combines the experimental statistical and systematic contributions, and the second is due to the uncertainty in the ratio of the Bs0 and the B+ fragmentation functions. No significant excess is observed for the decay B0→ μ+μ, and an upper limit of ℬ(B0 → μ+μ) < 3.6 × 10−10 is obtained at 95% confidence level. The Bs0→ μ+μ− effective lifetime is measured to be τμ+μ−=1.70−0.44+0.61 ps. These results are consistent with standard model predictions. [Figure not available: see fulltext.].

Original languageEnglish
Article number188
JournalJournal of High Energy Physics
Issue number4
Publication statusPublished - 1 Apr 2020
Externally publishedYes


  • B physics
  • Hadron-Hadron scattering (experiments)


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