Hunting for the heavy quark spin symmetry partner of Z${}_{cs}$

The discovery of a charged strange hidden-charm state Z${}_{cs}$(3985) implies another higher Z${}_{cs}^{\ast }$ state coupling to ${\overline{D}}_s^{\ast -}$D${}^{\ast 0}$ + c.c under the heavy quark spin symmetry. In this paper we discuss a possible hunt for it with data taken at existing facilities. We point out a hint for Z${}_{cs}^{\ast }$ in the data of ${\overline{B}}_s^0$$\to$ J/$\psi$K${}^{-}$K${}^{+}$ at LHCb, though weak, in line with the production mechanism of pentaquark P${}_c$. We also study the triangular singularity which would possibly enhance the production of Z${}_{cs}^{\ast }$ in electron-positron collision. Surprisingly, the production rate of Z${}_{cs}^{\ast }$ is expected to be maximum at the $e^{+}{e}^{-}$ center of mass energy of 4.648 GeV, which is lower than 4.681 GeV for Z${}_{cs}$ due to the inverted coupling hierarchy of D${}_{s1}{\overline{D}}^{\ast }$K and D${}_{s2}\overline{D}$K in the triangle diagrams. Their bottom analogue under heavy quark flavor symmetry is also discussed. Our theoretical analysis would confront with future experiment of LHCb, BESIII, and Bell II.