The CP -violating weak phase ϕs and the decay width difference ΔΓs between the light and heavy Bs0 mass eigenstates are measured with the CMS detector at the LHC in a sample of 48500 reconstructed Bs0→J/ψϕ(1020)→μ+μ−K+K− events. The measurement is based on a data sample corresponding to an integrated luminosity of 96.4 fb-1, collected in proton-proton collisions at √s=13 TeV in 2017–2018. To extract the values of ϕs and ΔΓs, 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 ΔΓs = 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, ΔΓs = 0.1032 ± 0.0095 (stat) ± 0.0048 (syst) ps-1, a significant improvement over the 8 TeV result.
Bibliographical note51 pages in total, author list starting page 35, 12 figures, 11 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/BPHY-2018-01/
- B physics