Dynamical study of hidden-strange pentaquarks as analogs of the hidden-charm states

TL;DR

Motivated by BESIII searches for hidden-strange exotics, the paper investigates nnss bar{s} pentaquarks using the QDCSM with the resonating-group method. By computing effective potentials and performing both single-channel and coupled-channel dynamical calculations, the study identifies three I=0 bound states with masses around $1759$, $2000$, and $2407$ MeV and a hidden-strange resonance $ΞK^{*}$ with $I(J^{P})=0(1/2^{-})$ near $2204$–$2208$ MeV and total width $55$–$63$ MeV; no bound states appear in the I=1 sector. Channel coupling is shown to be essential, enhancing short-range attraction and inducing meson-exchange contributions that enable bound states otherwise inaccessible in single channels. The results provide concrete targets for ongoing and future BESIII measurements and advance understanding of multiquark dynamics with strangeness.

Abstract

Motivated by the recent BESIII experiment~\cite{BESIII:2024muk} searching for hidden-strange exotic hadrons, we perform a systematic theoretical study of the hidden-strange pentaquark system within the framework of the quark delocalization color screening model (QDCSM) and the resonating group method (RGM). Our results demonstrate that the channel coupling effect plays a decisive role in the formation of bound and resonance states. It not only significantly enhances the short-range attraction but also induces essential attractive contributions from pion exchange. We predict three bound states with masses of $1759$ MeV, $2000$ MeV, and $2407$ MeV. Furthermore, we report the existence of a hidden-strange pentaquark resonance state, $ΞK^{\ast}$, with quantum numbers $I(J^{P})=0(1/2^{-})$. This resonance is identified in the $S$-wave scattering phase shifts of the $Λη_{s}$ and $Λφ$ open channels, with a predicted mass in the range of $2204\text{--}2208$ MeV. By accounting for both the scattering width from channel coupling and the intrinsic decay width of the constituent $K^{\ast}$, the total decay width is estimated to be $55\text{--}63$ MeV. These theoretical predictions provide important guidance for future experimental searches for such exotic states at facilities like BESIII.

Figures (5)

• Figure 1: Two parallel paths analogous to the hidden-charm sector for investigating hidden-strange pentaquark states, where $"n"$ denotes a $u$ or $d$ quark.
• Figure 2: The effective potentials calculated within the QDCSM, as defined in Eq. \ref{['Eq:PotentialV']}, for the $I=0$ hidden-strange pentaquark system. The panels correspond to the quantum numbers (a) $J^{P}=1/2^{-}$, (b) $J^{P}=3/2^{-}$, and (c) $J^{P}=5/2^{-}$, respectively. The curve labeled $CC$ denotes the effective potential obtained from the coupled-channel calculation.
• Figure 3: The effective potentials for the $I=1$ hidden-strange pentaquark system; the notation is the same as in Fig. \ref{['I=0-effective']}. The panels correspond to (a) $J^{P}=1/2^{-}$, (b) $J^{P}=3/2^{-}$, and (c) $J^{P}=5/2^{-}$.
• Figure 4: The low energy scattering phase shifts for the $I=0$ hidden-strange pentaquark system for various quantum numbers in the coupling channel estimation. $E_{cm}$ denotes the center-of-mass incident energy.
• Figure 5: The phase shifts of the open channels with two-channel coupling for I=0 in QDCSM. (a) corresponds to two-channel coupling with $\Lambda \eta_{s}$ and $\Xi K^{\ast}$, (b) denotes two-channel coupling with $\Lambda\phi$ and $\Xi K^{\ast}$, (c) is the two-channel coupling with $\Xi K$ and $\Xi K^{\ast}$.