Radiative Decays of Heavy-light Mesons and the $f_{H,H^*,H_1}^{(T)}$ Decay Constants

Understand

The on-shell matrix elements, or couplings $g_{H H^*(H_1)\gamma}$, describing the $B(D)_q^* \to B(D)_q \gamma$ and $B_{1 q} \to B_q \gamma$ ($q = u,d,s$) radiative decays, are determined from light-cone sum rules at next-to-leading order for the first time.

• Two different interpolating operators are used for the vector meson, providing additional robustness to our results.
• For the $D^*$-meson, where some rates are experimentally known, agreement is found.
• The couplings are of additional interest as they govern the lowest pole residue in the $B(D) \to \gamma$ form factors which in turn are connected to QED-corrections in leptonic decays $B(D) \to \ell \bar \nu$.