Rare radiative decay of the Ξ−b baryon

Recently, the LHCb collaboration established an upper experimental limit on the branching fraction of the rare radiative decay of the Ξ−b baryon: Br(Ξ−b → Ξ− γ)< 1.3x10^{-4}. The measured value is below the branching fraction predicted within the light-cone sum rules. In this paper, the process Ξ−b → Ξ− γ is investigated in the framework of the relativistic quark model, based on the quasi-potential approach in quantum field theory. Form factors are calculated with the consistent consideration of the relativistic effects. The obtained result for the decay branching fraction is below the upper experimental limit set by the LHCb, and is also consistent with some other theoretical calculations within error bars.