B meson distribution amplitude from B --> \gamma l \nu

Abstract

We reconsider the utility of the radiative decay $B\to \gamma \ell \nu$ with an energetic photon in the final state for determining parameters of the $B$-meson light-cone distribution amplitude. Including $1/m_b$ power corrections and radiative corrections at next-to-leading logarithmic order, we perform an improved analysis of the existing BABAR data. We find a provisional lower limit on the inverse moment of the $B$ meson distribution amplitude, ${\lambda }_B$, which, due to the inclusion of radiative and power corrections, is significantly lower than the previous result. More data with large photon energy is, however, required to obtain reliable results, as should become available in the future from SuperB factories.

Comments: 15 pages, 5 figures