Rare radiative B decays in perturbative QCD

Abstract

We report on recent progress on perturbative QCD calculations of certain exclusive rare weak $B$ meson decays involving hard photons. In the limit of a photon energy $E_γ$ much larger than $Λ_{QCD}$, the amplitudes for such processes can be analyzed in a twist expansion in powers of $Λ/E_γ$. The leading twist amplitude is given by the convolution of a hard scattering amplitude with the $B$ meson light-cone wavefunction. This approach is applied to a calculation of the leptonic radiative $B\to γ\ell ν_\ell$ formfactors and to an estimate of the weak annihilation contribution to the penguin decays $B\to ρ(ω)γ$. As an application we discuss a few methods for constraining the unitarity triangle with exclusive radiative B decays.