CP-violation studies at the HL-LHC with CMS using $\mathrm{B^0_s}$ decays to $\mathrm{J}/\psi\phi(1020)$

We have estimated the expected sensitivity on the CP-violating phase $\phi_s$ measured in the decay channel $\mathrm{B^0_s}~\to \! \mathrm{J}/\psi\phi(1020)$ in pp collisions with the CMS detector at the end of the HL-LHC data-taking with 3 ab$^{-1}$ of collected data. The sensitivity on $\phi_s$ mainly depends on the collected statistics, on the flavour-tagging power, and on the proper-decay-time resolution. The study is performed using fully simulated signal events and toy Monte Carlo experiments, for a few assumed tagging scenarios. The sensitivity on $\phi_s$ is expected to be in the 5-6 mrad range, which improves the current world average uncertainty by a factor of five.