An effective field theory model to describe nuclear matter in heavy-ion collisions

Relativistic mean field theory with means sigma, omega, pi and rho mediatin g interactions and nucleons as basic fermions has been very successful in d escribing nuclear matter and finite nuclei. However, in heavy-ion collision s, where the c. m. energy of two colliding nucleons will be in the hundreds of GeV region, nucleons are not expected to behave as point-like particles . Analyses of elastic pp and (p) over bar p scattering data in the relevant c. m. energy range show that the nucleon is a composite object - a topolog ical soliton or Skyrmion embedded in a condensed quark-antiquark ground sta te. Against this backdrop, we formulate an effective field theory model of nuclear matter based on the gauged linear sigma-model where quarks are the basic fermions, but the mesons still mediate the interactions. The model de scribes the nucleon as a Skyrmion and produces a q (q) over bar ground stat e analogous to a superconducting ground state. Quarks are quasi-particles i n this ground state. When the temperature exceeds a critical value, the sca lar field in the ground state vanishes, quarks become massless, and a chira l phase transition occurs leading to chiral symmetry restoration. We explor e the possibility of a first order phase transition in this model by introd ucing suitable self-interactions of the scalar field. Internal structures o f the Skyrmions are ignored, and they are treated as point-like fermions.