Scalar Mesons as qbar^2 q^2? Insight from the Lattice

TL;DR

This paper uses lattice QCD calculations to explore whether light scalar mesons are better described as four-quark states rather than traditional quark-antiquark pairs, providing insights into their structure.

Contribution

It presents the first lattice QCD evidence suggesting stable four-quark bound states for heavy quarks with specific quantum numbers, supporting the ar^2 q^2 model.

Findings

Indications of stable four-quark bound states for heavy quarks

Lattice calculations show non-exotic flavor quantum numbers

Supports ar^2 q^2 model for scalar mesons

Abstract

I describe some insight obtained from a lattice calculation on the possibility that the light scalar mesons are \qbar^2 q^2 states rather than \qbar q. First I review some general features of \qbar^2 q^2 states in QCD inspired quark models. Then I describe a lattice QCD calculation of pseudoscalar meson scattering amplitudes, ignoring quark loops and quark annihilation, which finds indications that for sufficiently heavy quarks there is a stable four-quark bound state with JPC=0{++} and non-exotic flavor quantum numbers.