Measurement of the $B_s \to J/\psi\phi$ Production Cross Section in $pp$ Collisions at $\sqrt{s} = 7$ TeV in the CMS experiment at LHC

I present measurements of the differential production cross section in bins of transverse momentum, $d\sigma/dp_T$, and rapidity, $d\sigma/d|y|$, for the decay $B_s \to J/\psi\phi$ in proton-proton collisions at $\sqrt{s} = 7$~TeV. The data correspond to an integrated luminosity of 40 pb$^{-1}$ collected by the Compact Muon Solenoid experiment operating at the CERN Large Hadron Collider in 2010. The $B_s$ decay is fully reconstructed with $J/\psi$ decaying into $\mu^+\mu^-$ and $\phi$ into $K^+K^-$. The cross section measurements are compared to several theoretical predictions.