The Quark–gluon–pion Plasma

While it is commonly believed that there is a direct transition from the hadronic to a quark-gluon phase at high temperature, it would be prejudicial to rule out a sequence of dynamically generated intermediate scales. Using as guide, an effective Lagrangian with unconfined gluons and constituent quarks, interacting with a chiral multiplet, we examine a scenario in which the system undergoes first-order transitions at T-comp, the compositeness scale of the pions, at T-chi, the scale for spontaneous chiral symmetry breaking, and at T-c, the confinement temperature. We find that at current energies, it is likely that the formation temperature of the plasma, T-0 < T-comp, and that this is, therefore, a quark-gluon-pion plasma (QGPP) rather than the usual quark-gluon plasma (QGP). We propose some dilepton-related signatures of this scenario. (C) 2002 Elsevier Science B.V. All rights reserved.