# Measurement of the B0s→μ+μ− branching fraction and effective lifetime and search for B0→μ+μ− decays

Abstract : A search for the rare decays B0s→μ+μ− and B0→μ+μ− is performed at the LHCb experiment using data collected in pp collisions corresponding to a total integrated luminosity of 4.4 fb−1. An excess of B0s→μ+μ− decays is observed with a significance of 7.8 standard deviations, representing the first observation of this decay in a single experiment. The branching fraction is measured to be B(B0s→μ+μ−)=(3.0±0.6+0.3−0.2)×10−9, where the first uncertainty is statistical and the second systematic. The first measurement of the B0s→μ+μ− effective lifetime, τ(B0s→μ+μ−)=2.04±0.44±0.05 ps, is reported. No significant excess of B0→μ+μ− decays is found and a 95 % confidence level upper limit, B(B0→μ+μ−)<3.4×10−10, is determined. All results are in agreement with the Standard Model expectations.
Document type :
Journal articles

http://hal.in2p3.fr/in2p3-01496133
Contributor : Claudine Bombar <>
Submitted on : Monday, March 27, 2017 - 11:16:22 AM
Last modification on : Wednesday, July 22, 2020 - 9:54:25 AM

### Citation

R. Aaij, L. Beaucourt, M. Chefdeville, D. Decamp, N. Déléage, et al.. Measurement of the B0s→μ+μ− branching fraction and effective lifetime and search for B0→μ+μ− decays. Physical Review Letters, American Physical Society, 2017, 118, pp.191801 ⟨10.1103/PhysRevLett.118.191801⟩. ⟨in2p3-01496133⟩

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