Radiative $Ξ_{b}^{-}\rightarrow Ξ^{-}γ$ decay

Recently, the LHCb Collaboration performed first search for the rare radiative $Ξ_{b}^{-}\rightarrow Ξ^{-}γ$ decay and put an upper limit, ${\cal B}(Ξ_{b}^{-}\to Ξ^{-}γ) < 1.3 \times 10^{-4}$, on its branching ratio. The measurement agrees well with existing theory prediction using SU(3) flavor symmetry method, but shows a slight tension with the previous prediction from light-cone sum rules. Inspired by this, we investigate this decay as well as other radiative decays of $Ξ_b^{0(-)}(Ξ^{'-}_{b})$ to $Ξ^{0(-)}$ and $Σ^{0(-)}$ baryons using the form factors calculated from light-cone QCD sum rules in full theory. we obtain ${\cal B}(Ξ_{b}^{-}\to Ξ^{-}γ)=1.08^{+0.63}_{-0.49} \times 10^{-5}$, which lies below the upper limit set by LHCb and is consistent with flavor-symmetry driven prediction. Our predictions on other channels may be checked in experiment and by other phenomenological approaches.

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