Chiral Symmetry and light resonances in hot and dense matter

TL;DR

This paper investigates how light meson resonances, like the sigma and rho, behave under hot and dense conditions, revealing their connection to chiral symmetry restoration and implications for nuclear physics and heavy-ion collisions.

Contribution

It introduces a chiral unitary framework to analyze the medium modifications of meson resonances and their scattering poles at finite temperature and density, including a microscopic many-body approach.

Findings

Resonance properties change significantly with temperature and density.

The rho meson experiences mass scaling and broadening in medium.

Evidence supports the molecular nature of pi-pi resonances.

Abstract

We present a study of the $\pi\pi$ scattering amplitude in the $\sigma$ and $\rho$ channels at finite temperature and nuclear density within a chiral unitary framework. Meson resonances are dynamically generated in our approach, which allows us to analyze the behavior of their associated scattering poles when the system is driven towards chiral symmetry restoration. Medium effects are incorporated in three ways: (a) by thermal corrections of the unitarized scattering amplitudes, (b) by finite nuclear density effects associated to a renormalization of the pion decay constant, and complementarily (c) by extending our calculation of the scalar-isoscalar channel to account for finite nuclear density and temperature effects in a microscopic many-body implementation of pion dynamics. Our results are discussed in connection with several phenomenological aspects relevant for nuclear matter and Heavy-Ion Collision experiments, such as $\rho$ mass scaling vs broadening from dilepton spectra and chiral restoration signals in the $\sigma$ channel. We also elaborate on the molecular nature of $\pi\pi$ resonances.