Search for the possible S=+1 Pentaquark states in Quenched Lattice QCD

TL;DR

This study uses quenched lattice QCD simulations to investigate the existence of an S=+1 pentaquark resonance, analyzing volume dependence to identify potential resonance states near the NK threshold.

Contribution

It introduces a method to search for S=+1 pentaquark states in quenched lattice QCD and provides evidence for a possible resonance slightly above the NK threshold.

Findings

Evidence suggests a resonance state near the NK threshold.

Volume dependence analysis supports the resonance interpretation.

Successfully extracted energies of low-lying states in the specified quantum channel.

Abstract

We study spin $\frac12$ hadronic states in quenched lattice QCD to search for a possible $S=+1$ pentaquark resonance. Simulations are carried out on $8^3\times 24$, $10^3\times 24$, $12^3\times 24$ and $16^3\times 24$ lattices at $\beta$=5.7 at the quenched level with the standard plaquette gauge action and the Wilson quark action. We adopt a Dirichlet boundary condition in the time direction for the quark to circumvent the possible contaminations due to the (anti)periodic boundary condition for the quark field, which are peculiar to the pentaquark. By diagonalizing the $2\times 2$ correlation matrices constructed from two independent operators with the quantum numbers $(I,J)=(0,\frac12)$, we successfully obtain the energies of the lowest state and the 2nd-lowest state in this channel. The analysis of the volume dependence of the energies and spectral weight factors indicates that a resonance state is likely to exist slightly above the NK threshold in $(I,J^P)=(0,\frac12^-)$ channel.