Light-cone sum rules for $B \to π$ form factors revisited

Abstract

We reconsider and update the QCD light-cone sum rules for $B\to π$ form factors. The gluon radiative corrections to the twist-2 and twist-3 terms in the correlation functions are calculated. The $\bar{MS}$ $b$-quark mass is employed, instead of the one-loop pole mass used in the previous analyses. The light-cone sum rule for $f^+_{Bπ}(q^2)$ is fitted to the measured $q^2$-distribution in $B\to πl ν_l$, fixing the input parameters with the largest uncertainty: the Gegenbauer moments of the pion distribution amplitude. For the $B\to π$ vector form factor at zero momentum transfer we predict $f^+_{Bπ}(0)= 0.26^{+0.04}_{-0.03}$. Combining it with the value of the product $|V_{ub}f^+_{Bπ}(0)|$ extracted from experiment, we obtain $|V_{ub}|=(3.5\pm 0.4\pm 0.2\pm 0.1) \times 10^{-3}$. In addition, the scalar and penguin $B\to π$ form factors $f^0_{Bπ}(q^2)$ and $f^T_{Bπ}(q^2)$ are calculated.

33 pages, 7 figures, one figure and a few comments added, version to appear in JHEP