Measurement of the mixing-induced and CP-violating parameters of $B_s^0 \to \phi\gamma$ decays at LHCb

This thesis presents the first measurement of the mixing-induced and CP-violating parameters of the $B_s^0 \to \phi\gamma$ decay ($\mathcal{A}^{\Delta}_{\phi\gamma}$, $\mathcal{S}_{\phi\gamma}$ and $\mathcal{C}_{\phi\gamma}$) appearing in the time-dependent decay rate, using the data collected by the LHCb experiment during the 2011 and 2012 data taking periods, accounting for a total of 3 fb$^{-1}$ integrated luminosity.