\(D_q^*\rightarrow D_q \gamma \) : Probing the Inner Structure of Charm Mesons

The distribution amplitudes (DAs) for a heavy quark system are not known well and are very challenging. One tries to model them using heavy quark effective field theory. However, there is a free parameter involved which is related to the inverse moments of DAs. Its value needs to be fixed using some experimental data. For the case of B-meson, it is done using the information on the \(B \rightarrow \ell \nu _\ell \gamma \) process which helps us in limiting its value by providing limits. For the case of D-meson, the uncertainty in its value is very large which leads to huge uncertainties in the non-perturbative hadronic quantities like form factors. In this talk, we shed some light on these issues and discussed a possible solution using the experimental data of \(D_q^*\rightarrow D_q \gamma \) \((q=u,d,s)\) decays and comparing them with the results obtained using Light Cone Sum Rules. We will show how such an estimation can provide better and complementary results for these unknown parameters.