Lattice study of light scalar tetraquarks with I=0,2,1/2,3/2: are sigma and kappa tetraquarks?

TL;DR

This lattice study investigates whether the light scalar mesons sigma and kappa are tetraquarks by analyzing their spectrum in various isospin channels using dynamical and quenched simulations, finding potential tetraquark states in some channels.

Contribution

The paper presents the first lattice QCD analysis of light scalar tetraquark candidates sigma and kappa across multiple isospin channels, using both dynamical and quenched simulations with different quark formulations.

Findings

Identified additional light states in I=0 and I=1/2 channels consistent with sigma and kappa.

No extra light states found in I=2 and I=3/2 channels, supporting their non-resonant nature.

Qualitative agreement between dynamical and quenched simulation results.

Abstract

We investigate whether the lightest scalar mesons sigma and kappa have a large tetraquark component, as is strongly supported by many phenomenological studies. A search for possible light tetraquark states with J^PC=0^++ and I=0, 2, 1/2, 3/2 on the lattice is presented. We perform the two-flavor dynamical simulation with Chirally Improved quarks and the quenched simulation with overlap quarks, finding qualitative agreement between both results. The spectrum is determined using the generalized eigenvalue method with a number of tetraquark interpolators at the source and the sink, and we omit the disconnected contractions. The time-dependence of the eigenvalues at finite temporal extent of the lattice is explored also analytically. In all the channels, we unavoidably find lowest scattering states pi(k)pi(-k) or K(k)pi(-k) with back-to-back momentum k=0, 2*pi/L,... However, we find an additional light state in the I=0 and I=1/2 channels, which may be interpreted as the observed resonances sigma and kappa with a sizable tetraquark component. In the exotic repulsive channels I=2 and I=3/2, where no resonance is observed, we find no light state in addition to the scattering states.