Abstract
The decays Bs0→μ+μ− and B0→μ+μ− are highly suppressed in the standard model constituting sensitive probes of new physics. We present the results of a search for these rare decays in proton-proton collisions using the full data sample collected by the CMS experiment during LHC Run I. Through a fit to the dimuon invariant-mass spectrum, an excess of events with respect to the background is observed, compatible with the Bs0(B0) signal with a significance of 4.3 (2.0) standard deviations (σ). The measured branching fractions are B(Bs0→μ+μ−)=(3.0−0.9+1.0)×10−9 and B(B0→μ+μ−)=(3.5−1.8+2.1)×10−10. The combination of the CMS and LHCb results, using their full Run I data samples, yield an event excess compatible with the Bs0(B0) signal with a significance in excess of 6σ(3σ). The ongoing and projected accelerator and detector upgrades will allow to establish and to carry out precision measurements of both rare decays, and explore novel observables with further sensitivity to new physics effects.
Highlights
Pre-LHC searches and experimental statusThe ARGUS [8], UA1 [9], CLEO [10], Belle [11], BaBar [12], CDF [13], D0 [14], ATLAS [15], CMS [16], and LHCb [17] experiments have all published limits on these decays
The decays B0s → μ+μ− and B0 → μ+μ− are highly suppressed in the standard model constituting sensitive probes of new physics
The predicted SM values corresponding to the decay-time integrated branching fractions are B(B0s → μ+μ−)SM = (3.57 ± 0.30) × 10−9 and B(B0 → μ+μ−)SM = (1.07 ± 0.10) × 10−10 [3, 4], where the uncertainties are fully dominated by nonpertubrative QCD effects determined through lattice studies
Summary
The ARGUS [8], UA1 [9], CLEO [10], Belle [11], BaBar [12], CDF [13], D0 [14], ATLAS [15], CMS [16], and LHCb [17] experiments have all published limits on these decays. In the last couple of years, Tevatron’s CDF [13] and LHC’s LHCb [18] have both reported double-sided intervals for B(B0s → μ+μ−). Notwithstanding, sufficient statistical sensitivity for the B0s decay needed to wait for the BR UL(95% CL) or measurement
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