Homogeneous nucleation of quark-gluon plasma, finite size effects, and long-lived metastable objects

The general formalism of homogeneous nucleation theory is applied to study the hadronization pattern of the ultrarelativistic quark-gluon plasma (QGP) undergoing a first order phase transition. A coalescence model is proposed to describe the evolution dynamics of hadronic clusters produced in the nucleation process. The size distribution of the nucleated clusters is important for the description of the plasma conversion. The model is most sensitive to the initial conditions of the QGP thermalization, time evolution of the energy density, and the interfacial energy of the plasma-hadronic matter interface. The rapidly expanding QGP is first supercooled by about ΔT=T-T_c=4–6%. Then it reheats again up to the critical temperature T_c. Finally it breaks up into hadronic clusters and small droplets of plasma. This fast dynamics occurs within the first 5–10 fm/c. The finite size effects and fluctuations near the critical temperature are studied. It is shown that a drop of longitudinally expanding QGP of the transverse radius below 4.5 fm can display a long-lived metastability. However, both in the rapid and in the delayed hadronization scenarios, the bulk pion yield is emitted by sources as large as 3–4.5 fm. This may be detected experimentally both by a Hanbury–Brown-Twiss interferometry signal and by the analysis of the rapidity distributions of particles in narrow p_T intervals at small |p_T| on an event-by-event basis.