Light-Cone Sum Rules for the $D_{(s)}\to {\eta }^{(\prime )}l{\nu }_l$ Form Factor

Abstract

We present an improved light-cone sum rule analysis of the decay form factors of $D$ and $D_s$ into $\eta$ and ${\eta }^{\prime }$ and argue that these decays offer a very promissing possibility to determine the leading Fock-state gluonic contribution of the ${\eta }^{\prime }$ at future experimental facilities as FAIR or Super-KEKB. We also give the corresponding branching ratios for B decays.

Comments: 10 pages, 5 figures, Minor wording changes and some references added, results unchanged