The sigma meson ($f_0$) at finite temperature with truncated overlap fermions
We study the temperature dependence of meson screening masses in two-flavour lattice QCD using dynamical truncated overlap fermions, a type of lattice chiral fermions. The screening masses for the $π$, $ρ$, $a_1$, $a_0$, and the sigma $(f_0)$ mesons are extracted by computing spatial correlation functions. This exploratory study uses meson screening masses and the connected/disconnected decomposition of the scalar correlator as diagnostic observables to examine how the disconnected contribution changes across the pseudocritical region. Above the pseudocritical temperature $T_{\rm pc}$, the $π$ and $f_0$ screening masses become degenerate, consistent with chiral restoration. The $(ρ,a_1)$ pair also shows 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 truncated overlap fermion simulations can capture the qualitative thermal behaviour of the scalar sector.