The radiative charmed baryon decay Ξc20∗ å

U-spin symmetry (s ↔ d symmetry) forbids the radiative decay Ξc20∗ å Ξc10γ in the SU(3) limit. The quark mass term breaks U-spin symmetry and the leading nonanalytic contribution to the radiative decay amplitude is computable in heavy baryon chiral perturbation theory. The radiative decay branching ratio is determined by the coupling constant g2 and at leading order in chiral perturbation theory is given by Brc2(Ξ0∗ å Ξc10γ) = 1.0 × 10−3g22. Measurement of this branching fraction will determine ∥g2∥.