Measurement of the $P_1$ and $P_5'$ angular parameters of the decay $\mathrm{B}^0 \to \mathrm{K}^{*0} \mu^+ \mu^-$ in proton-proton collisions at $\sqrt{s}=8~\mathrm{TeV}$

The angular distributions of the decay $\mathrm{B}^0 \to \mathrm{K}^{*0} \mu^ +\mu^-$ are studied using data corresponding to an integrated luminosity of $20.5~\mathrm{fb}^{-1}$ collected with the CMS detector at the LHC in proton-proton collisions at $\sqrt{s} = 8~\mathrm{TeV}$. An angular analysis gives access to many physical observables, including $P_5'$, which is of particular interest due to measurements from the LHCb Collaboration, that exibit potential discrepancy with the standard model. Based on a sample of 1397 signal events, the $P_1$ and $P_5'$ angular parameters are determined as a function of the dimuon invariant mass squared. The measurement are in agreement with standard model predictions.