Hidden-charm tetraquarks with strangeness in the chiral quark model

Abstract

The LHCb collaboration has recently announced the discovery of two hidden-charm pentaquark states with also strange quark content, Pcs(4338) and Pcs(4459); its analysis points towards having both hadrons isospin equal to zero and spin-parity quantum numbers 1 2 − and 3 2 − , respectively. We perform herein a systematical investigation of the qqscc (q = u, d) system by means of a chiral quark model, along with a highly accurate computational method, the Gaussian expansion approach combined with the complex-scaling technique. Baryon-meson configurations in both singletand hidden-color channels are considered. The Pcs(4338) and Pcs(4459) signals can be well identified as molecular bound states with dominant components ΛJ/ψ (60%) and ΞcD (23%) for the lowest-energy case and ΞcD * (72%) for the highest-energy one. Besides, it seems that some narrow resonances can be also found in each allowed I(J P )-channel in the energy region of 4.6 − 5.5 GeV, except for the 1( 1 2 − ) where a shallow bound state with dominant Ξ * c D * structure is obtained at 4673 MeV with binding energy EB = −3 MeV. These exotic states are expected to be confirmed in future high energy experiments.

An updated review of the new hadron states

“…See Refs. [743,509,744,745] for more quark model calculations within the diquark-antidiquark picture, and there also exist some quark model calculations [746,210,747,748] considering both meson-meson and diquark-antidiquark structures.…”

Aspects of $Z_{cs}(3985)$ and $Z_{cs}(4000)$

“…Thus, whether they are two different states or not, and how to decode their inner structures are now pretty much the agenda for theorists. So far, there are some discussions of their inner structures with various theoretical methods [41,42,43,44,45,46,47,48,49,50]. The most papular interpretation of Z cs (3985)/Z cs (4000) is explaining them as two different states: DD * s /D * D s molecular states [43,48] or compacted tetraquark states ccsū with different spin-parity [41,44,49].…”

Investigation of the bottom analog of the Zcs(3985) state

“…More recently, the LHCb Collaboration reported two charmonium-like states with strangeness , named Z cs (4000) + and Z cs (4220) + , in the J/ψK invariant mass spectrum [55], where the mass of the former one is similar to the one of Z cs (3985) observed by BESIII Collaboration. Similar to the case of Z b (10610) and Z c (3900)/Z c (3885), the observed masses of Z cs (3985)/Z cs (4000) are close to the threshold of D * s D, the properties of Z cs (3985)/Z cs (4000) have been investigated in molecular [56][57][58][59][60][61][62][63][64][65][66] and tetraquark [67][68][69][70][71][72] scenarios.…”