Resonant Singly Heavy Pentaquarks in the MIT Bag Model: Mass Spectra and Strong Decays

TL;DR

This work investigates singly heavy pentaquarks within the MIT bag model, focusing on confinement scales, mass spectra, and strong-decay properties. By incorporating chromomagnetic and color-electric interactions and solving a variational problem for the bag radius, the study predicts pentaquark masses typically about $\sim$500 MeV above their mirror-baryon ground states and places their bag radii near the lattice-QCD confinement window $\sim$1.17–1.29 fm. The analysis shows most states lie above baryon–meson thresholds and are strongly unstable, though a subset exhibits narrow widths due to threshold effects or flavor-symmetry constraints. A detailed color-spin basis framework and S-wave decay formalism are developed to map pentaquark configurations to final-state channels, enabling predictions of decay patterns and resonance-like behavior that warrant lattice verification and experimental search.

Abstract

Exploring the limits of color interactions in multiquark states is an important topic. Based on the bag confinement picture of hadrons, we find that for singly heavy pentaquarks, the bag confinement radius precisely falls within the range of color interaction limits provided by lattice QCD, approximately 1.17--1.29$\,\text{fm}$. This leads us to believe that singly heavy pentaquark states have the potential to form resonant states. Inspired by singly heavy baryons, we consider the mirror pentaquarks of singly heavy baryons. Furthermore, we adopt the MIT bag model, taking into account chromomagnetic and color-electric interactions between heavy and strange quarks, to calculate the mass spectrum of singly heavy pentaquarks configured as $qqqQ\bar{q}$ and analyze the stability of their S-wave two-body strong decays. We show that for the singly heavy pentaquark system, the masses are generally about $500\, \text{MeV}$ higher than the corresponding mirror baryon ground state masses, which is consistent with conclusions drawn from chiral methods. We also provide a mass mapping relationship between singly heavy pentaquarks and singly heavy baryons based on light quark flavor symmetry. The analysis of strong decays indicates that these singly heavy pentaquarks are unstable with respect to strong decays, which is consistent with our initial hypothesis.

Figures (1)

• Figure 1: Bag confinement energy curve, with the red region corresponding to a resonance scale interval.