Quark-gluon plasma and mixed phase in an aggregation-percolation model

The mixed phase (mixture between pieces of quark-gluon plasma and hadronic matter) occurring in the formation, and hadronization, of the quark-gluon plasma is studied within the framework of percolation approaches. Starting from a gas of nucleon bags, and, at finite temperature, of pion bags, the transition from a hadronic gas to a quark-gluon plasma is calculated using a restructuring aggregation model. The key parameter of this approach is the quark confinement radius of the nucleon. In the hadronization process we start from the MIT bag model description of the quark-gluon plasma and study the mixed phase using a 3-dimensional site-bond percolation model on a cubic lattice. The key parameter of this approach is the bag constant B. These two complementary descriptions of the mixed phase are discussed and compared together. (orig.)