Photon polarization in B → Xγ in the standard model

The standard model prediction for the B̄⁰ → X _s,dγ 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/(4π), and in exclusive decays by Δ_QCD/m _b. The suppression is not stronger in B̄⁰ → X_dγ decays than it is in B̄⁰ → X _sγ. We estimate that the time dependent CP asymmetries in B → K*γ, ργ, K_sπ⁰γ, and π⁺π^-γ are of order 0.1 and that thev have significant uncertainties.