Eur. Phys. J. C (2009) 61: 879-892
https://doi.org/10.1140/epjc/s10052-008-0831-z

Regular Article - Theoretical Physics

Chiral symmetry and light resonances in hot and dense matter

Departamento de Física Teórica II, Univ. Complutense, 28040, Madrid, Spain

^* e-mail: gomez@fis.ucm.es

Received: 14 August 2008
Published online: 16 December 2008

Abstract

We present a study of the π π scattering amplitude in the σ and ρ 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 ρ mass scaling versus broadening from dilepton spectra and chiral restoration signals in the σ channel. We also elaborate on the molecular nature of π π resonances.