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 $E_{\gamma }$ much larger than ${\Lambda }_{QCD}$, the amplitudes for such processes can be analyzed in a twist expansion in powers of $\Lambda /E_{\gamma }$. 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 $B\to \gamma \ell {\nu }_{\ell }$ formfactors and to an estimate of the weak annihilation contribution to the penguin decays $B\to \rho (\omega )\gamma$. As an application we discuss a few methods for constraining the unitarity triangle with exclusive radiative B decays.

Comments: 11 pages, 3 included figures. Invited talk given at the 5th International Workshop on Particle Physics Phenomenology, Chi-Pen, Taitung, Taiwan, 8-11 Nov 2000