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

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 $T_{\mathrm{pc}}$, 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 $T_{\mathrm{pc}}$, while the disconnected part becomes significant below $T_{\mathrm{pc}}$, 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.

9 pages, 9 figures and 2 tables