Measurement of the CP-violating phase ?s in the Bs 0?J/??(1020)??+??K+K? channel in proton-proton collisions at s=13TeV

Abstract

The CP -violating weak phase ?<inf>s</inf> and the decay width difference ??<inf>s</inf> between the light and heavy B<inf>s</inf> 0 mass eigenstates are measured with the CMS detector at the LHC in a sample of 48500 reconstructed B<inf>s</inf> 0?J/??(1020)??+??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=13TeV in 2017–2018. To extract the values of ?<inf>s</inf> and ??<inf>s</inf>, a time-dependent and flavor-tagged angular analysis of the ?+??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 ?<inf>s</inf>=?11±50(stat)±10(syst)mrad and ??<inf>s</inf>=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=8TeV, the following values are obtained: ?<inf>s</inf>=?21±44(stat)±10(syst)mrad, ??<inf>s</inf>=0.1032±0.0095(stat)±0.0048(syst)ps?1, a significant improvement over the 8 TeV result. © 2021 The Author(s)