B physics with upgraded detector

The CMS potential for B-Physics with the Upgraded Phase-I and Phase-II detectors will be discussed, with the $\mathrm{B}_{s}^{0}\to\mu^{+}\mu^{-}$ and $\mathrm{B}^{0}\to\mu^{+}\mu^{-}$ benchmark channels, for the runs of the LHC at $\sqrt{s}=14$~TeV up to an integrated luminosity of 3000~$\mathrm{fb}^{-1}$. With the upgraded CMS detector it will be possible to efficiently trigger and reconstruct both processes, with reduced statistical and systematic uncertainties leading to high precision measurements of the branching fractions of the $\mathrm{B}^{0}\to\mu^{+}\mu^{-}$ and $\mathrm{B}_{s}^{0}\to\mu^{+}\mu^{-}$ decays. This will allow in turn stringent tests of the Standard Model