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

Abstract

The 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.

An updated review of the new hadron states

“…57. Many other theoretical studies [729,730,731,732,733,734,735,736] also suggest the existence of some exotic structure near the D * D * s threshold around 4.1 GeV, so further experimental and theoretical studies are demanded to examine whether the Z cs (4220) is an effect of an event dip around the D * D * s threshold. Besides the above theoretical studies, the interpretation of the Z cs (3985) and/or Z cs (4000) states as the D D * s /D * Ds hadronic molecular state(s) was supported by many other theoretical studies [737,738].…”

Observation of a Charged Charmoniumlike Structure in e+e−→π+π−J/ψ at s=4.26 GeV

“…There are still ongoing debates on whether these particles are the same state or not [41,[45][46][47][48][49][50][51][52]. Therefore, to enhance our comprehension of these Z cs states and explore the possibility of new Z cs states, it is imperative to conduct further measurements of e + e − → KZ cs → K KJ/ψ [39,47,[51][52][53][54][55][56] In this Letter, a measurement of the Born cross sections of the process e + e − → K + K − J/ψ is presented at center-of-mass (c.m.) energies from 4.61 to 4.95 GeV [57], corresponding to an integrated luminosity of 5.85 fb −1 [58].…”

Photo- and electro-production of narrow exotic states: from light quarks to charm and up to bottom

“…Surprisingly, it would be produced under lower center-of-mass (c.m.) energy of e + e − than that of Z cs due to the inverted coupling hierarchy of triangular singularity at electron-positron annihilation [103]. This prediction would be confirmed by increasing the amount of collected events at BESIII.…”

“…So it is essential to hunt for it at running and future facilities. Its clue is weakly traced in the data of B0 s → J/ψK − K + at LHCb [103] and e + e − → K + D * − s D * 0 + c.c. at BESIII [104].…”