Radiative decays of the spin-$2$ partner of $X(3872)$

Pan-Pan Shi, Jorgivan M. Dias, Feng-Kun Guo

It has been generally expected that the $X(3872)$ has a spin-2 partner, $X_2$, with quantum numbers $J^{PC}=2^{++}$. In the hadronic molecular model, its mass was predicted to be b…