Measurement of the CP-violating phase ϕs in the Bs0→J/ψϕ(1020)→μ+μ−K+K− channel in proton-proton collisions at s=13TeV

Abstract

The CP-violating weak phase φsand the decay width difference s between the light and heavy B0smass eigenstates are measured with the CMS detector at the LHC in a sample of 48 500 reconstructed B0s→J/ψφ(1020) →μ+μ−K+K−events. The measurement is based on a data sample corresponding to an integrated luminosity of 96.4fb−1, collected in proton-proton collisions at √s=13 TeV in 2017–2018. To extract the values of φs and s, a time-dependent and flavor-tagged angular analysis of the μ+μ−K+K−final state is performed. The analysis employs a dedicated tagging trigger and a novel opposite-side muon flavor tagger based on machine learning techniques. The measurement yields φs=−11 ±50 (stat)±10 (syst) mrad and s=0.114 ±0.014 (stat)±0.007 (syst) ps−1, in agreement with the standard model predictions. When combined with the previous CMS measurement at √s=8 TeV, the following values are obtained: φs=−21 ±44 (stat)±10 (syst) mrad, s=0.1032 ±0.0095 (stat)±0.0048 (syst) ps−1, a significant improvement over the 8TeV result.

A.M. Sirunyan et al., Measurement of the CP-violating phase ϕs in the Bs0→J/ψϕ(1020)→μ+μ−K+K− channel in proton-proton collisions at s=13TeV, Physics Letters B