Photon polarization in B→Xγ in the standard model -: art. no. 011504

The standard model prediction for the (B) over bar (0)-->X(s,d)gamma decay amplitude with a right-handed photon is believed to be tiny, suppressed by m(s,d)/m(b), compared to the amplitude with a left-handed photon. We show that this suppression is fictitious: In inclusive decays, the ratio of these two amplitudes is only suppressed by g(s)/(4pi), and in exclusive decays by Lambda(QCD)/m(b). The suppression is not stronger in (B) over bar (0)-->X(d)gamma decays than it is in (B) over bar (0)-->X(s)gamma. We estimate that the time dependent CP asymmetries in B-->K(*)gamma, rhogamma, K(S)pi(0)gamma, and pi(+)pi(-)gamma are of order 0.1 and that they have significant uncertainties.