The Spectra of $p\barΛ$ and $p\barΣ$ Hexaquark States

TL;DR

This paper investigates the near-threshold spectra of baryon–antibaryon hexaquark molecules formed by $p\bar{\Lambda}$ and $p\bar{\Sigma}$ using QCD sum rules. By constructing two independent baryon currents and analyzing two-point correlators with an operator-product expansion up to dimension $13$, the authors extract ground-state masses and decay constants for six molecular configurations with $J^{P}=0^{-},0^{+},1^{-}$, finding them all below corresponding dibaryon thresholds. The results disfavor a pure $p\bar{\Lambda}$ or $p\bar{\Sigma}$ interpretation for $X(2085)$, while the $J^{P}=1^{-}$ states lie near $X(2075)$, suggesting possible components of these observed states and highlighting the need for further investigation and decay-mode studies. The work also provides predictions for strong- and weak-decay patterns that can guide future experiments at BESIII, Belle II, and LHCb in identifying or constraining such hexaquark states, and discusses potential mixing with other hadronic configurations as a caveat and avenue for refinement.

Abstract

Motivated by the observation of the $J^P = 1^+$ resonance $X(2085)$ in the $p\barΛ$ system by the BESIII collaboration, we studied the molecular states of hexaquarks $p\barΛ$ and $p\barΣ$ with baryon-antibaryon structures within the framework of the QCD sum rules. Non-perturbative contributions up to dimension 13 were considered in our analysis. The results indicate the existence of six possible molecular states $p\barΛ$ and $p\barΣ$, with quantum numbers $J^{P}=0^{-}, 0^{+}, 1^{-}$. Consequently, the current sum rule results do not support the interpretation of $X(2085)$ as a $p\barΛ$ or $p\barΣ$ molecular state. On the other hand, we find that the masses of the proposed $p\barΛ$ and $p\barΣ$ structures with $J^{P} = 1^{-}$ are in the vicinity of observed $X(2075)$, which implies that the nature of this state needs more invistigations. Moreover, the possible decay modes of the concerned hexaquark states are analyzed.

Figures (8)

• Figure 1: Typical Feynman diagrams for the two-point correlation functions, where the thick lines represent light quarks, the spiral lines denote gluons, and the solid dots indicate the condensates. The diagrams include contributions from the perturbative term, quark condensates, gluon condensates, and mixed condensates.
• Figure 2: The figures for the $0^{-}$$p\bar{\Lambda}$ state.
• Figure 3: The figures for the $0^{+}$$p\bar{\Lambda}$ state.
• Figure 4: The figures for the $1^{-}$$p\bar{\Lambda}$ state.
• Figure 5: The figures for the $0^{-}$$p\bar{\Sigma}$ state.