Extrapolating SU(3) breaking from D to B decays - art. no. 077301

We consider two SU(3) breaking parameters R-1(m(B)) and R-2(m(B)) appearing in a relation between B+ --> K pi and B+ --> pi pi amplitudes, which plays an important role in determining the weak phase gamma. In the heavy quark limit, we identify an isospin-related quantity R-2(m(D)) measured in D deca ys, exhibiting large SU(3) breaking which is likely due to nonfactorizable effects. Applying heavy quark symmetry to semileptonic D and B decay form f actors, we find that factorizable SU(3) breaking in R-2(m(B))/R-1(m(B)) may be significantly larger than estimated from certain model calculations of form factors.