# Thermal behaviors of light scalar resonances at low temperatures

## TL;DR

This paper investigates how the masses and widths of light scalar meson resonances change with temperature using unitarized chiral perturbation theory, revealing significant mass decreases for some resonances at high temperatures.

## Contribution

It provides a detailed analysis of the thermal evolution of scalar resonances within a unitarized $U(3)$ chiral framework, including resonance pole behavior at finite temperature.

## Key findings

- The $\sigma$ and $\kappa$ masses decrease significantly with temperature.
- The widths of $\sigma$ and $\kappa$ remain large around 200 MeV.
- The $f_0(980)$ and $a_0(980)$ are less affected by temperature.

## Abstract

We study the thermal properties of the lowest multiplet of the QCD light-flavor scalar resonances, including the $f_0(500)/\sigma$, $K_{0}^{*}(700)/\kappa$, $f_0(980)$ and $a_0(980)$, in the framework of unitarized $U(3)$ chiral perturbation theory. After the successful fits to the meson-meson scattering inputs, such as the phase shifts and inelasticities, we obtain the unknown parameters and further calculate the resonance poles and their residues at zero temperature. By including the finite-temperature effects in the unitarized meson-meson scattering amplitudes, the thermal behaviors of the scalar resonance poles in the complex energy plane are studied. The masses of $\sigma$ and $\kappa$ are found to considerably decrease when increasing the temperatures, while their widths turn out to be still large when the temperatures reach around $200$ MeV. In contrast, both the masses and widths of the $f_0(980)$ and $a_0(980)$ are only slightly changed.