First observation of the radiative decay $Lambda_{b}^{0} to Lambda gamma$

The radiative decay $Lambda_{b}^{0} to Lambda gamma$ is observed for the first time using a data sample of proton-proton collisions corresponding to an integrated luminosity of $1.7,fb^{-1}$ collected by the LHCb experiment at a center-of-mass energy of $13,TeV$. Its branching fraction is measured exploiting the $B^{0} to K^{*0} gamma$ decay as a normalization mode and is found to be $mathcal{B}(Lambda_{b}^{0} to Lambda gamma)= (7.1 pm 1.5 pm 0.6 pm 0.7) times 10^{-6}$, where the quoted uncertainties are statistical, systematic and systematic from external inputs, respectively. This is the first observation of a radiative decay of a beauty baryon.