LHCb: Rare Decays at LHCb

The decay modes $B_d\to K^*\gamma$ and $B_s \to \phi \gamma$ are promising laboratories for the search of New Physics effects, their properties being particularly sensitive to the presence of new heavy particles that may propagate virtually within the one-loop process involved in penguin diagrams. The penguin $B_s \to \phi \gamma$ decay has been observed by Belle with rather poor precision, $\mathcal{B}$($B_s \to \phi \gamma$) = 57$^{+22}_{-19}$ x 10$^{-6}$, therefore, additional measurements are expected for this channel. With a data sample corresponding to an integrated luminosity of ~36 pb$^{-1}$ collected in 2010, a clear and promising signal has been observed for the $B_d\to K^*\gamma$. The mass resolution is dominated by the electromagnetic calorimeter energy resolution (ECAL is inter-calibrated at the ~2% level). A first hint of the $B_s \to \Phi \gamma$  decay has also been observed. Given this preliminary results and the theory predictions, we expect that, with the data we will record in 2011, the measurement of the ratio of branching fractions for $B_s \to \Phi \gamma$ and $B_d\to K^*\gamma$ can be done with a statistical precision of less than 5%.