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

Abstract

AbstractThe discovery of a charged strange hidden-charm state $$Z_{cs}$$ Z cs (3985) implies another higher $$Z^*_{cs}$$ Z cs ∗ state coupling to $${\bar{D}}_s^{*-}D^{*0} + c.c$$ D ¯ s ∗ - D ∗ 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 $$Z^*_{cs}$$ Z cs ∗ in the data of $${\bar{B}}_s^0 \rightarrow J/\psi K^- K^+$$ B ¯ s 0 → J / ψ K - K + at LHCb, though weak, in line with the production mechanism of pentaquark $$P_c$$ P c . We also study the triangular singularity which would possibly enhance the production of $$Z^*_{cs}$$ Z cs ∗ in electron-positron collision. Surprisingly, the production rate of $$Z^*_{cs}$$ Z cs ∗ is expected to be maximum at the $$e^+ e^-$$ e + e - center of mass energy of 4.648 GeV, which is lower than 4.681 GeV for $$Z_{cs}$$ Z cs due to the inverted coupling hierarchy of $$D_{s1}{\bar{D}}^* K$$ D s 1 D ¯ ∗ K and $$D_{s2}{\bar{D}}K$$ D s 2 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.