Study of the rare decays of B s 0 and B 0 mesons into muon pairs using data collected during 2015 and 2016 with the ATLAS detector

Collaboration, ATLAS and Barton, A.E. and Bertram, I.A. and Borissov, G. and Bouhova-Thacker, E.V. and Fox, H. and Henderson, R.C.W. and Jones, R.W.L. and Kartvelishvili, V. and Long, R.E. and Love, P.A. and Muenstermann, D. and Parker, A.J. and Smizanska, M. and Tee, A.S. and Walder, J. and Wharton, A.M. and Whitmore, B.W. (2019) Study of the rare decays of B s 0 and B 0 mesons into muon pairs using data collected during 2015 and 2016 with the ATLAS detector. Journal of High Energy Physics, 2019 (4): 98. ISSN 1029-8479

Abstract

A study of the decays B s 0 → μ + μ − and B 0 → μ + μ − has been performed using 26.3 fb −1 of 13 TeV LHC proton-proton collision data collected with the ATLAS detector in 2015 and 2016. Since the detector resolution in μ + μ − invariant mass is comparable to the B s 0 -B 0 mass difference, a single fit determines the signal yields for both decay modes. This results in a measurement of the branching fraction ℬ(Bs0→μ+μ−)=(3.2−1.0+1.1)×10−9 and an upper limit ℬ (B→ μ + μ − ) <4.3 × 10 − 10 at 95% confidence level. The result is combined with the Run 1 ATLAS result, yielding ℬ(Bs0→μ+μ−)=(2.8−0.7+0.8)×10−9 and ℬ (B→ μ + μ − ) <2.1 × 10 − 10 at 95% confidence level. The combined result is consistent with the Standard Model prediction within 2.4 standard deviations in the ℬ(B0→μ+μ−)−ℬ(Bs0→μ+μ−) plane.[Figure not available: see fulltext.] © 2019, The Author(s).