Lattice investigation of the scalar mesons a_0(980) and \kappa\ using four-quark operators

TL;DR

This study explores the internal structure of scalar mesons a_0(980) and kappa using lattice QCD with four-quark operators, finding no evidence of tetraquark or molecular states beyond scattering states.

Contribution

First lattice QCD investigation employing four-quark operators to analyze scalar mesons a_0(980) and kappa, focusing on their possible tetraquark or molecular nature.

Findings

Spectrum consistent with two-particle scattering states

No evidence for tetraquark or molecular bound states

Analysis based on connected contributions only

Abstract

We carry out an exploratory study of the isospin one a0(980) and the isospin one-half kappa scalar mesons using Nf=2+1+1 Wilson twisted mass fermions at one lattice spacing. The valence strange quark is included as an Osterwalder-Seiler fermion with mass tuned so that the kaon mass matches the corresponding mass in the unitary Nf=2+1+1 theory. We investigate the internal structure of these mesons by using a basis of four-quark interpolating fields. We construct diquark-diquark and molecular-typecinterpolating fields and analyse the resulting correlation matrices keeping only connected contributions. For both channels, the low-lying spectrum is found to be consistent with two-particle scattering states. Therefore, our analysis shows no evidence for an additional state that can be interpreted as either a tetraquark or a tightly-bound molecular state.