The sigma meson ($f_0$) at finite temperature with truncated overlap fermions

TL;DR

This study investigates how meson screening masses in lattice QCD change with temperature, showing chiral symmetry restoration and the dominance of connected contributions in the scalar sector above the pseudocritical temperature.

Contribution

It demonstrates that dynamical truncated overlap fermions can effectively capture the thermal behavior of meson screening masses and chiral symmetry restoration in lattice QCD.

Findings

Degeneracy of $ ho$ and $a_1$ screening masses above $T_{pc}$

Degeneracy of $ ext{pi}$ and $f_0$ screening masses above $T_{pc}$

Connected contributions dominate the $f_0$ propagator above $T_{pc}$

Abstract

We study the temperature dependence of meson screening masses in two-flavour lattice QCD using dynamical truncated overlap fermions (TOF), a type of lattice chiral fermions. The screening masses for the $\pi$, $\rho$, $a_1$, $a_0$, and the sigma $(f_0)$ mesons are extracted by computing spatial correlation functions. Above the pseudocritical temperature $T_{\rm pc}$, the $\pi$ and $f_0$ screening masses become degenerate, consistent with chiral restoration. The $(\pi,f_0)$ and $(\rho,a_1)$ pairs also show the expected degeneracy. Decomposition of the $f_0$ propagator reveals that the connected contribution dominates above $T_{\rm pc}$, while the disconnected part becomes significant below $T_{\rm pc}$, explaining the reduced statistical clarity observed at low $T$. These results demonstrate that dynamical TOF simulations can capture the qualitative thermal behaviour of the scalar sector.