B meson wave function from the B→γlν decay -: art. no. 014003

We show that the leading-power B meson wave function can be extracted reliably from the photon energy spectrum of the B ->gamma l nu decay up to O(1/m(b)(2)) and O(alpha(s)(2)) uncertainty, m(b) being the b quark mass and alpha(s) the strong coupling constant. The O(1/m(b)) corrections from heavy-quark expansion can be absorbed into a redefined leading-power B meson wave function. The two-parton O(1/m(b)) corrections cancel exactly, and the three-parton B meson wave functions turn out to contribute at O(1/m(b)(2)). The constructive long-distance contribution through the B -> V ->gamma transition, V being a vector meson, almost cancels the destructive O(alpha(s)) radiative correction. Using models of the leading-power B meson wave function available in the literature, we obtain the photon energy spectrum in the perturbative QCD framework, which is then compared with those from other approaches.