These proceedings describe the measurement of the CP-violating phase ϕs using B0s→J/ψϕ(1020) decays with the CMS experiment at √s=13~TeV.
The measurement is based on a data sample collected in 2017--2018 corresponding to an integrated luminosity of 96.4~fb−1.
A dedicated tagging trigger and a opposite-side muon flavour tagger based on deep learning techniques have been used in this analysis, significantly increasing the fraction of tagged events.
The decay width (mass) difference ΔΓs (Δms) between the light and heavy B0s mass eigenstates, the B0s average decay width Γs and the CP violation observable |λ| are also measured.
The combination with the results obtained by CMS at √s=8~TeV is also presented.