CP-violation in the decay B0,B 0→π+π−γ

The decay B 0→π+π−γ has a bremsstrahlung component determined by the amplitude for B 0→π+π−, as well as a direct component determined by the penguin interaction VtbVtd∗c7O7. Interference of these amplitudes produces a photon energy spectrum dΓ/dx=ax+b+c1x+c2x2+⋯ (x=2Eγ/mB) where the terms c1,2 contain a dependence on the phase αeff=π−arg[(VtbVtd∗)∗A(B 0→π+π−)]. We also examine the angular distribution of these decays, and show that in the presence of strong phases, an untagged B0/B 0 beam can exhibit an asymmetry between the π+ and π− energy spectra.