Search for New Physics with Rare Heavy Flavour Decays at LHCb

The LHCb experiment has the potential, during the 2010-11 run, to observe the rare decay $B_s^0\to {\mu }^{+}{\mu }^{-}$ or improve significantly its exclusion limits. This study will provide very sensitive probes of New Physics (NP) effects. High sensitivity to NP contributions is also achieved by measuring photon polarization by performing a time dependent analysis of $B_s^0\to \varphi \gamma$, and by an angular study of the decay $B_d^0\to K^{\ast 0}{\mu }^{+}{\mu }^{-}$. Preparations for these analyses are presented and studies shown of how existing data, for example prompt $J\mathrm{/}\psi$ events, can be used to validate the analysis strategy.