LONG DISTANCE EFFECTS AND CP VIOLATION in $B^{\pm }\to {\rho }^{\pm }\gamma$

We demonstrate that the long distance contribution to $B^{\pm} \to \rho^{\pm} \gamma$ may have a large effect on the decay rate and through it on the CP violating partial rate asymmetry. The change in the asymmetry can be between a factor of 0.4 and 1.4 with respect to the effect of the short distance contribution alone, depending on the values of the CKM parameters $\rho$ and $\eta$ .