Critical behavior and resonance excitation in the thermodynamics of extended hadrons

A system of spatially extended non-interacting hadrons generally leads at sufficiently high density to a phase transition from “gas” to “solid”. Here we study the effect of interaction, in form of an exponential resonance excitation spectrum (dual resonance model, statistical bootstrap model), on this phenomenon. While the presence of resonances significantly lowers the critical temperature, the finite size of the hadrons prevents the occurrence of the thermodynamic singularity associated with an exponential resonance spectrum in the case of point-like constituents.