Radiative decays \bm{$D^*_{(s)}\to D_{(s)}\gamma$} in covariant confined quark model

Abstract

Radiative decays $D^*_{(s)}\to D_{(s)}\gamma$ are revisited in light of new experimental data from \textit{BABAR} and BESIII collaborations. The radiative couplings $g_{D^*D\gamma}$ encoding nonperturbative QCD effects are calculated in the framework of the covariant confined quark model developed by us. We compare our results with other theoretical studies and experimental data. The couplings (in $\textrm{GeV}^{-1}$) $|g_{D^{*+}D^+\gamma}| = 0.45(9)$ and $|g_{D^{*0}D^0\gamma}| = 1.72(34)$ calculated in our model agree with the experimental data $|g_{D^{*+}D^+\gamma}|=0.47(7)$ and $|g_{D^{*0}D^0\gamma}|=1.77(16)$. The most interesting case is the decay $D^*_s\to D_s\gamma$, for which the recent prediction based on light-cone sum rules at next-to-leading order $|g_{D^*_s D_s\gamma}|=0.60(19)$ deviates from the first (and so far the only) lattice QCD result $|g_{D^*_s D_s\gamma}|=0.11(2)$ at nearly $3\sigma$. Our calculation yields $|g_{D^*_s D_s\gamma}|=0.29(6)$, which falls somehow between the two mentioned results, but is larger than those predicted in other studies using quark models or QCD sum rules. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Article funded by SCOAP3 and published under licence by Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Science and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.