Predictions on $B\to \pi \bar{l}{\nu }_l$, $D\to \pi \bar{l}{\nu }_l$ and $D\to K\bar{l}{\nu }_l$ from QCD Light-Cone Sum Rules

Abstract

The $f^{+}$ form factors of the $B\to \pi$, $D\to \pi$ and $D\to K$ transitions are calculated from QCD light-cone sum rules (LCSR) and used to predict the widths and differential distributions of the exclusive semileptonic decays $B\to \pi \bar{l}{\nu }_l$, $D\to \pi \bar{l}{\nu }_l$ and $D\to K\bar{l}{\nu }_l$, where $l=e,\mu$. The current theoretical uncertainties are estimated. The LCSR results are found to agree with the results of lattice QCD calculations and with experimental data on exclusive semileptonic D decays. Comparison of the LCSR prediction on $B\to \pi \bar{l}{\nu }_l$ with the CLEO measurement yields a value of |V_{ub}| in agreement with other determinations.

Comments: 24 pages, 12 figures, Latex, epsfig, some additional remarks on the two-pole parameterization, prediction on the $B\to K$ form factor added, version to appear in Phys. Rev. D