Anisotropic Lattice QCD Studies of Penta-quark Anti-decuplet

TL;DR

This study uses anisotropic lattice QCD to investigate penta-quark states, finding the negative parity state close to experimental values but identifying it as a scattering state rather than a resonance.

Contribution

It introduces a new hybrid boundary condition method to distinguish compact penta-quark resonances from scattering states in lattice QCD.

Findings

Negative parity state near 1.75 GeV, close to experimental value

The negative parity state is identified as an NK scattering state

Positive parity state found at about 2.25 GeV, too heavy for Theta^+(1540)

Abstract

Anti-decuplet penta-quark baryon is studied with the quenched anisotropic lattice QCD for accurate measurement of the correlator. Both the positive and negative parity states are studied using a non-NK type interpolating field with I=0 and J=1/2. After the chiral extrapolation, the lowest positive parity state is found at m_{Theta} \simeq 2.25 GeV, which is too massive to be identified with the experimentally observed Theta^+(1540). The lowest negative parity state is found at m_{Theta}\simeq 1.75 GeV, which is rather close to the empirical value. To confirm that this state is a compact 5Q resonance, a new method with ``hybrid boundary condition (HBC)'' is proposed. The HBC analysis shows that the observed state in the negative parity channel is an NK scattering state.