$Z_{cs}$ states from the $D_s^{\ast }{\bar{D}}^{\ast }$ and $J/\psi K^{\ast }$ coupled channels: Signal in $B^{+}\to J/\psi \varphi K^{+}$ decay

Abstract

We study the $D_s^{\ast }{\bar{D}}^{\ast }$ system in connection with the $J/\psi K^{\ast }$ in coupled channels and observe that, within reasonable values of the cut-off used to regularize the loops, the system does not develop a bound state. However, the $J^P=2^{+}$ channel has enough attraction to create a strong cusp structure that shows up in the $J/\psi K^{+}$ invariant mass distribution in the $B^{+}\to J/\psi \varphi K^{+}$ decay at the $D_s^{\ast }{\bar{D}}^{\ast }$ threshold. Such structure is visible in the experimental $B^{+}\to J/\psi \varphi K^{+}$ and ${\bar{B}}^0\to J/\psi K^{+}{K}^{-}$ decays, with small statistics, and our results should stimulate further measurements around this region, given the fact that cusp effects provide as valuable information on hadron dynamics as resonances themselves.

Comments: 14 pages, 11 figures, 1 table: minor modifications