Chiral symmetry breaking and chemical equilibrium in heavy-ion collisions

We examine the thermalization of an ensemble of the octet of pseudoscalar mesons, in the isospin symmetric limit, whose interactions are constrained through chiral symmetry, unitarity, and measurements. We use unitarized reaction amplitudes from next-to-leading-order chiral perturbation theory which generate all resonances up to masses of about 2 GeV, with 12 input parameters, namely, f(pi), three masses, and eight low-energy constants of chiral perturbation theory. In linear response theory, we find that the relaxation time is around 100 fm at a temperature of 150 MeV and increases rapidly with temperature. The long relaxation times are directly related to the fact that these mesons are pseudo-Goldstone bosons of chiral symmetry breaking.