Search for $B^0_s \to \mu \mu$ and $B^0 \to \mu \mu$ at LHCb

A search for the decays $B^0_s \to \mu \mu$ and $B^0 \to \mu \mu$ is performed with about 37 pb$^{-1}$ of $pp$ collisions at $\sqrt{s}$ = 7 TeV collected by the LHCb experiment at the Large Hadron Collider at CERN. The observed numbers of events are consistent with the background expectations. The resulting upper limits on the branching fractions are B$(B^0_s \to \mu \mu$) < 5.6 \times 10$^{-8}$ and B$(B^0 \to \mu \mu)$ < 1.5 \times 10$^{-8}$ at 95% confidence level.