Abstract
The observation by BESIII and LHCb of states with hidden charm and open strangeness ($c\bar c q\bar s$) presents new opportunities for the development of a global model of heavy-quark exotics. Here we extend the dynamical diquark model to encompass such states, using the same values of Hamiltonian parameters previously obtained from the nonstrange and hidden-strange sectors. The large mass splitting between $Z_{cs}(4000)$ and $Z_{cs}(4220)$ suggests substantial SU(3)$_{\rm flavor}$ mixing between all $J^P \! = \! 1^+$ states, while their average mass compared to that of other sectors offers a direct probe of flavor octet-singlet mixing among exotics. We also explore the inclusion of $\eta$-like exchanges within the states, and find their effects to be quite limited. In addition, using the same diquark-mass parameters, we find $P_c(4312)$ and $P_{cs}(4459)$ to fit well as corresponding nonstrange and open-strange pentaquarks.
Highlights
The spectrum of known heavy-quark exotic hadrons continues to expand frequently, with about 50 candidates observed to date
Almost all have a valence light-flavor content consisting of only q ≡ u and d quarks, but very recently some states with open strangeness have been detected in both the open-charm [1,2] and hiddencharm sectors
Both a pentaquark [3] state and tetraquark [4,5] states have been observed.1. Multiple reviews summarizing both experimental and theoretical advances in this field have appeared in recent years [6,7,8,9,10,11,12,13,14,15,16]
Summary
The spectrum of known heavy-quark exotic hadrons continues to expand frequently, with about 50 candidates observed to date. Almost all have a valence light-flavor content consisting of only q ≡ u and d quarks, but very recently some states with open strangeness have been detected in both the open-charm [1,2] (cdsu) and hiddencharm sectors In the latter, both a pentaquark [3] (ccuds) state and tetraquark [4,5] (ccus) states have been observed.. BESIII observes a structure [4] in the Kþ recoil spectrum of eþe− → KþðD−s DÃ0 þ DÃs−D0Þ near the two-charmed-meson thresholds (about 3975 and 3977 MeV, respectively). For this Zcsð3985Þ state, they obtain mZ−cs 1⁄4 3982.5þ−21..68.
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