Long-distance contribution to s->d gamma and implications for Omega(-)->Xi(-)gamma, B-s->B*(d)gamma, and b->s gamma

We estimate the long-distance (LD) contribution to the magnetic part of the s-->d gamma transition using the vector meson dominance approximation (V=rho,omega,psi(i)). We find that this contribution may be significantly larger than the short-distance (SD) contribution to s-->d gamma and could possibly saturate the present experimental upper bound on the Omega(-)-->Xi(-)gamma decay rate, Gamma(Omega---><(Xi>-gamma)(max)similar or equal to 3.7x10(-9) eV. For the decay B-s-->B*(d) gamma, which is driver by s-->d gamma as well, we obtain an upper bound on the branching ratio B(B-s-->B*(d) gamma)<3x10(-8) from Gamma(Omega--->Xi-gamma)(max). Barring the possibility that the quantum chromodynamics coefficient alpha(2)(m(s)(2)) is much smaller than 1, Gamma(max Omega--->Xi-gamma) also implies the approximate relation 2/3 Sigma(i)g(psi i)(2)(0)/m(psi i)(2)similar or equal to 1/2g(rho)(2)(0)/m(rho)(2)+1/6g(omega)(2)(0)/m(omega)(2). This relation agrees quantitatively with a recent independent estimate of the left-hand side by Deshpande, He, and Trampetic, confirming that the LD contributions to b-->s gamma are small. We find that these amount to an increase of (4+/-2)% in the magnitude of the b-->s gamma transition amplitude, relative to the SD contribution alone.