Study of B --> \mu^+ \nu_\mu and K_s^0 --> \mu^+ \mu^- decays

In this report my work done during the CERN Summer Student Programme within the LHCb collaboration is summarized. Results obtained on B --> \mu^+ \nu_\mu and K_s^0 --> \mu^+ \mu^- analyses are presented. For the first, the dominant background modes were studied and fitted to data. For the second, the efficiencies of the stripping cuts were calculated, and the dominant background mode studied and fitted.