Measurement of decay width difference ∆Γs and weak phase difference ∆Φs in the decay channel of B0s → J/ψφ using CMS data We are going to do the study of CP-violation of doubly Cabibbo suppressed decay channel B0s → J/ψφ at centre of mass energy √ s = 13TeV using CMS data, where a pseudo-scalar meson B0s decays to two vector meson J/ψ and φ. The measurement of decay width difference of ∆Γs and weak phase difference ∆Φs will be performed in this study.