A lattice study of the pentaquark states

TL;DR

This lattice QCD study investigates pentaquark states, analyzing volume dependence of spectral weights to determine the existence of resonances, and finds no definitive evidence for a pentaquark resonance within current data accuracy.

Contribution

First lattice QCD analysis using spectral weight volume dependence to study pentaquark states, highlighting challenges in identifying resonances.

Findings

Cannot exclude a pentaquark resonance within current data

Mass in negative parity channel close to KN threshold

Positive parity mass about 60% above threshold

Abstract

We present a study of the pentaquark system in quenched lattice QCD using diquark-diquark and kaon-nucleon local and smeared interpolating fields. We examine the volume dependence of the spectral weights of local correlators on lattices of size $16^3\times 32$, $24^3\times32$ and $32^3\times 64$ at $\beta=6.0$. We find that a reliable evaluation of the volume dependence of the spectral weights requires accurate determination of the correlators at large time separations. Our main result from the spectral weight analysis in the pentaquark system is that within our variational basis and statistics we can not exclude a pentaquark resonance. However our data also do not allow a clear identification of a pentaquark state since only the spectral weights of the lowest state can be determined to sufficient accuracy to test for volume dependence. In the negative parity channel the mass extracted for this state is very close to the KN threshold whereas in the positive parity channel is about 60% above.