Search for the radiative $$ {\Xi}_b^{-} $$ → Ξ−γ decay

The first search for the rare radiative decay $$ {\Xi}_b^{-} $$ Ξ b − → Ξ−γ is performed using data collected by the LHCb experiment in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb−1. The $$ {\Xi}_b^{-} $$ Ξ b − → Ξ−J/ψ channel is used as normalization. No $$ {\Xi}_b^{-} $$ Ξ b − → Ξ−γ signal is found and an upper limit of $$ \mathcal{B} $$ B ($$ {\Xi}_b^{-} $$ Ξ b − → Ξ−γ) < 1.3 × 10−4 at 95% confidence level is obtained.