Implications of the Zcs(3985) and Zcs(4000) as two different states

Abstract

Recently, the hidden charm tetraquark states Z_cs(3985) and Z_cs(4000) with strangeness were observed by the BESIII and LHCb collaborations, respectively, which are great breakthroughs for exploring exotic quantum chromodynamics (QCD) structures. The first and foremost question is whether they are the same state. In this work, we explore the implications of the narrower state Z_cs(3985) in BESIII and the wider one Z_cs(4000) in LHCb as two different states. Within a solvable nonrelativistic effective field theory, we include the possible violations of heavy quark spin symmetry and SU(3) flavor symmetry in a comprehensive approach. If Z_cs(3985) and Z_cs(4000) are two different states, our results show that Z_cs(4000)/Z_cs(3985) is the pure (|D‾_s^∗D〉+/-|D‾_sD^∗〉)/2 state, and the SU(3) flavor partner of Z_c(3900) is Z_cs(4000) rather than the Z_cs(3985). Another two important consequences are the existence of a tensor D‾_s^∗D^∗ resonance with mass about 4126 MeV and width 13 MeV, and the suppression of the decay mode Z_cs(3985)→J/ψK. The two consequences can be tested in experiments and distinguish the two-state interpretation from the one-state scheme.

Keywords: states; Heavy quark spin symmetry; Strangness; Tetraquark.