Radiative decays at LHCb

LHC$b$ will seek to test the Standard Model of Particle Physics and confirm or constrain many of the new physics (NP) models by making precision measurements on the radiative decays of B-mesons. Radiative transitions in neutral B meson decays, such as $b \to s\gamma$ and $b \to d\gamma$, are very sensitive to NP, 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 polarization of emitted photons in radiative decays is particularly interesting as the $\overline{B}(B)$ meson decays predominantly into a left (right)-handed photon. The branching ratio of the $B_d \to K^{*}\gamma$ decay mode, measured first by CLEO then updated by Babar and Belle is precisely known, $\cal{B}(B_d)$ = (43.3 $\pm$ 1.5) x 10$^{-6}$, thus, its measurement at LHCb will be crucial for the calorimeter calibration and can be used as control channel for other radiative decays. The penguin $B_s \to \phi\gamma$ decay has been observed by Belle, with a $\cal{B}(B_s \to \phi\gamma$) = 57$^{+22}_{-19}$ x 10$^{-6}$.