Semileptonic charm decays $D \to \pi l \nu_{\l}$ and $D \to K l \nu_l$ from QCD Light-Cone Sum Rules

Understand

We present a new calculation of the $D\to\pi$ and $D \to K$ form factors from QCD light-cone sum rules.

• The $\overline{MS}$ scheme for the $c$-quark mass is used and the input parameters are updated.
• The results are $f^+_{D\pi}(0)= 0.67^{+0.10}_{-0.07}$, $f^+_{DK}(0)=0.75^{+0.11}_{-0.08}$ and $f^+_{D\pi}(0)/f^+_{DK}(0)=0.88 \pm 0.05$.
• Combining the calculated form factors with the latest CLEO data, we obtain $|V_{cd}|=0.225\pm 0.005 \pm 0.003 ^{+0.016}_{-0.012}$ and $|V_{cd}|/|V_{cs}|= 0.236\pm 0.006\pm 0.003\pm 0.013$ where the first and second errors are of experimental origin and the third error is due to the estimated uncertainties of our calculation.