Search for the Theta^+(1540) in lattice QCD

TL;DR

This study uses lattice QCD with improved techniques to search for the pentaquark Theta^+(1540), finding no evidence for its positive parity state but observing signals consistent with scattering states.

Contribution

The paper applies chirally improved fermions and Jacobi smearing in lattice QCD to investigate the Theta^+ pentaquark, providing new insights into its possible existence.

Findings

No evidence for positive parity Theta^+

Detected signals compatible with nucleon-kaon scattering

Results for negative parity are inconclusive

Abstract

We report on a study of the pentaquark Theta^+(1540), using a variety of different interpolating fields. We use Chirally Improved fermions in combination with Jacobi smeared quark sources to improve the signal and get reliable results even for small quark masses. The results of our quenched calculations, which have been done on a 12^3 x 24 lattice with a lattice spacing of a = 0.148 fm, do not provide any evidence for the existence of a \Theta^+ with positive parity. We do observe, however, a signal compatible with nucleon-kaon scattering state. For the negative parity the results are inconclusive, due to the potential mixture with nucleon-kaon and N^*-kaon scattering states.