Temperature effects on the electromagnetic couplings of pions in hot hadronic matter are studied with an effective chiral Lagrangian. We show that the Ward-Takahashi identity is satisfied at non-zero temperature in the soft pion limit. The in-medium electromagnetic form factor of the pion is obtained in the time-like region and shown to be reduced in magnitude, especially near the vector-meson resonance region. Finally, we discuss the consequences of this medium effect on dilepton production from hot hadronic matter.
We calculate characteristic time scales for chemical equilibration of pions
in hot hadronic matter using an effective chiral Lagrangian. We find that
inelastic processes involving the vector and axial vector mesons reduce the
chemical equilibration time by a factor of $\sim 10$ compared to the result
previously calculated in chiral perturbation theory. For a temperature of
$T\sim 150 MeV$ we obtain a chemical relaxation time of $\tau_{ch} \simeq 10
fm/c$, which is comparable with typical time scales for a hadronic system
generated in SPS-energy heavy ion collisions. The effect of baryons is also
estimated and found to be negligible for SPS-energies but important for
AGS-energies. We predict, that chemical freeze-out should take place at
considerable higher temperatures $\Delta T \simeq 20 MeV$ than thermal
freeze-out and that the hadronic phase would not sustain a pion chemical
potential larger than $100 MeV$.Comment: (include Tex source file
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.