First measurements of radiative $B$ decays in LHCb

Radiative decays of $B$ mesons are interesting for the study of physics beyond the Standard Model, as they are an example of FCNC. In order to effectively study radiative $B$ decays, good trigger performance is needed. Two trigger strategies have been studied, one exclusive and one inclusive: one one side, the already existing exclusive lines have been modified, and, on the other side, a new set of inclusive topological lines, specific for radiative $B$ decays, has been introduced. Their performance in 2011 has been assessed both on simulation and on data, and the strategy for 2012 has been outlined. The full 2011 dataset collected by LHCb has been used to extract the ratio of branching fractions $\cal{B}(B^0 \to K^{*0}\gamma)/\cal{B}(B^0_s\to\phi\gamma)$, which has been measured to be 1.31 $\pm$ 0.08,$(\text{stat})\pm$ 0.04,$(\text{syst})\pm$ 0.10,$(f_s/f_d)$. From this result, and using the well-known value for $B^0\to K^{*0}\gamma$, the branching fraction of $B^0_s\to\phi\gamma$ has been found to be (3.3 $\pm$ 0.3 )\times 10$^{-5}$, largely improving previous results.