Eur. Phys. J. C (2022) 82: 161
https://doi.org/10.1140/epjc/s10052-022-10055-z

Regular Article - Theoretical Physics

Hunting for the heavy quark spin symmetry partner of $Z_{\mathit{cs}}$

¹ Institute of Modern Physics, Chinese Academy of Sciences, 730000, Lanzhou, China
² University of Chinese Academy of Sciences, 100049, Beijing, China
³ School of Physics, University of Electronic Science and Technology of China, 610054, Chengdu, China

^b zhiyang@uestc.edu.cn

Received: 20 October 2021
Accepted: 25 January 2022
Published online: 21 February 2022

Abstract

The discovery of a charged strange hidden-charm state $Z_{\mathit{cs}}$(3985) implies another higher $Z_{\mathit{cs}}^{\ast }$ 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 $Z_{\mathit{cs}}^{\ast }$ 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 $Z_{\mathit{cs}}^{\ast }$ in electron-positron collision. Surprisingly, the production rate of $Z_{\mathit{cs}}^{\ast }$ 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 $Z_{\mathit{cs}}$ 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.