Particle Production in Matter at Extreme Conditions

We study particle production and its density evolution and equilibration in hot dense medium. One type of hot dense medium, which we study, is hadronic gas produced at quark gluon plasma hadronization in heavy ions collisions in SPS, RHIC and LHC experiments. We study hadron production at non-equilibrium quark gluon plasma hadronization and their evolution in thermal hadronic gas phase. We use non-equilibrium hadronization as the initial condition in the study of hadronic kinetic phase. During this time period some hadronic resonances can be produced in lighter hadrons fusion. Production of resonances is dominant over decay if there is non-equilibrium excess of decay products. Within this model we explain apparently contradictory experimental results reported in RHIC experiments: Sigma(1385) yield is enhanced while Lambda(1520) yield is suppressed compared to the statistical hadronization model expectation obtained without kinetic phase. We also predict Delta(1232) enhancement. The second type of plasma medium we consider is the relativistic electron positron photon plasma drop. This plasma is expected to be produced in decay of supercritical field created in ultrashort laser pulse. We study at what conditions this plasma drop is opaque for photons and therefore may reach thermal and chemical equilibrium. Further we consider muon and pion production in this plasma also as a diagnostic tool. Finally all these theoretical developments can be applied to begin a study of particles evolution in early universe in temperatures domain from QGP hadronization (160 MeV) to nucleosynthesis (0.1 MeV). The first results on pion equilibration are presented here.