Strong and electromagnetic decays in the long-distance to identify the structure of the $T_{cc}^+$

Lu Meng, Guang-Juan Wang, Bo Wang, Shi-Lin Zhu

Published 2021-07-30Version 1

Very recently, the LHCb Collaboration reported the doubly charmed tetraquark state $T_{cc}^+$ blow the $D^{*+}D^0$ threshold about $273$ keV. As a very near-threshold state, its long-distance structure is very important. In the molecular scheme, we investigate the kinetic allowed strong decays $T_{cc}^+\to D^0D^0\pi^+$, $T_{cc}^+\to D^+D^0\pi^0$ and radiative decays $D^+D^0 \gamma$, which are sensitive to the long-range structure of $T_{cc}^+$. In a coupled-channel effective field theory, we extract the coupling constants of $T_{cc}^+$ to $D^{*0}D^+$ and $D^{*+}D^0$ channels from the residuals of the $T$-matrix. Due to the low-energy universality, the coupling constants only depend on the binding energy. With the coupling constants and the strong and radiation vertices of $D^*$ meson from experiments, we give the strong and radiative decay widths of $T_{cc}^+$. Our predictions can be used to test the inner structure of $T_{cc}^+$ state.