Penta-Quark Anti-Decuplet in Anisotropic Lattice QCD

TL;DR

This study uses anisotropic lattice QCD to investigate penta-quark states, finding that the observed states are likely scattering states rather than true resonances, with masses higher than the experimentally observed Theta^+(1540).

Contribution

First high-precision lattice QCD study of penta-quark Theta^+ using anisotropic lattices and non-NK interpolating fields, clarifying its possible resonance nature.

Findings

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

Negative parity state at ~1.75 GeV, likely a scattering state

Negative parity state close to empirical value but not a resonance

Abstract

The penta-quark(5Q) Theta^+(1540) is studied in anisotropic lattice QCD with renormalized anisotropy a_s/a_t=4 for a high-precision measurement. Both the positive and the negative parity 5Q baryons 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 heavy to be identified with Theta^+(1540). In the negative parity channel, the lowest energy state is found at m_{Theta}\simeq 1.75 GeV. Although it is rather close to the empirical value, it is considered to be an NK scattering state rather than a localized resonance state.