Measurement of the CP-violating phase phi_s in the Bs0 to J/psi phi(1020) to mu+ mu− K+ K− channel in proton-proton collisions at sqrt(s) = 13 TeVстатья
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Дата последнего поиска статьи во внешних источниках: 4 июня 2021 г.
Аннотация:The CP-violating weak phase ϕs and the decay width difference ΔΓs between the light and heavy B0s mass 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 96.4 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.