Measurement of the CP-violating phase phi_s in the Bs -> J/Psi phi channel at 13 TeV by CMS

Abstract

These proceedings present the measurement of the weak CP-violating phase $\phi_s$ in the $B_s^0\to J/\psi\,\phi(1020)$ decay channel at $\sqrt{s} = 13$ TeV with the CMS experiment. The measurement is based on a data sample corresponding to an integrated luminosity of 96.4 fb$^{-1}$, collected in 2017--2018. This analysis employs a dedicated tagging trigger and a novel opposite-side muon flavor tagger based on deep learning techniques. The decay width (mass) difference $\Delta\Gamma_s$ ($\Delta m_s$) between the light and heavy $B_s^0$ mass eigenstates, the $B_s^0$ average decay width $\Gamma_s$ and the CP violation observable $\left| \lambda \right|$ are also measured. The combination with the results obtained by CMS at $\sqrt{s}=8$ TeV is also presented.