Penta-quark in Anisotropic Lattice QCD

TL;DR

This study uses anisotropic lattice QCD with a novel boundary condition method to investigate penta-quark states, finding that the observed negative-parity state is likely an NK scattering state rather than a compact resonance.

Contribution

The paper introduces the hybrid boundary condition method to distinguish between scattering states and genuine resonances in lattice QCD studies of penta-quarks.

Findings

The lowest-lying positive-parity penta-quark state is around 2.25 GeV.

The lowest-lying negative-parity state is around 1.75 GeV.

The negative-parity state observed is identified as an NK scattering state.

Abstract

Penta-quark (5Q) baryons are studied using anisotropic lattice QCD for high-precision measurement of temporal correlators. A non-NK-type interpolating field is employed to study the 5Q states with J^P=1/2^{\pm} and I=0. In J^P=1/2^+ channel, the lowest-lying state is found at m_{5Q} \simeq 2.25 GeV, which is too massive to be identified as the Theta^+(1540). In J^P=1/2^- channel, the lowest-lying state is found at m_{5Q} \simeq 1.75 GeV. To distinguish a compact 5Q resonance state from an NK scattering state, a new method with ``hybrid boundary condition (HBC)'' is proposed. As a result of the HBC analysis, the observed state in the negative-parity channel turns out to be an $NK$ scattering state.