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.
Journal of High Energy Physics
- Pub Date:
- April 2020
- B physics;
- Hadron-Hadron scattering (experiments);
- High Energy Physics - Experiment
- Replaced with the published version. Added the journal reference and the DOI. All the figures and tables, including additional supplementary figures, can be found at http://cms-results.web.cern.ch/cms-results/public-results/publications/BPH-16-004 (CMS Public Pages)