Predictions on $\overrightarrow{B}\pi \overline{l}{\nu }_l,$ $\overrightarrow{D}\pi \overline{l}{\nu }_l,$ and $\overrightarrow{D}K\overline{l}{\nu }_l$ from QCD light-cone sum rules

The $f^{+}$ form factors of the $\overrightarrow{B}\pi ,$ $\overrightarrow{D}\pi$ and $\overrightarrow{D}K$ transitions are calculated from QCD light-cone sum rules (LCSRs) and used to predict the widths and differential distributions of the exclusive semileptonic decays $\overrightarrow{B}\pi \overline{l}{\nu }_l,$ $\overrightarrow{D}\pi \overline{l}{\nu }_l$ and $\overrightarrow{D}K\overline{l}{\nu }_l,$ 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 of $\overrightarrow{B}\pi \overline{l}{\nu }_l$ with the CLEO measurement yields a value of $|V_{\mathrm{ub}}|$ in agreement with other determinations.