Metastable quark-antiquark droplets within the Nambu-Jona-Lasinio model

Chemically nonequilibrated quark-antiquark matter is studied within the Nam bu-Jona-Lasinio model. The equations of state of nonstrange (q = u,d) and s trange (q = s) q (q) over bar systems are calculated in the mean-field appr oximation. The existence of metastable bound states with zero pressure is p redicted at finite densities and temperatures T less than or similar to 50 MeV. It is shown that the minimum energy per pal-ride occurs for symmetric systems, with equal densities of quarks and antiquarks. At T = 0 these meta stable states have quark number densities of about 0.5 fm(-3) for q = u,d a nd of 1 fm(-3) for q = s. A first order chiral phase transition is found at finite densities and temperatures. The critical temperature for this phase transition is approximately 75 MeV (90 MeV) for the nonstrange (strange) b aryon-free quark-antiquark matter. For realistic choices of parameters, the model does not predict a phase transition in chemically equilibrated syste ms. Possible decay channels of the metastable q (q) over bar droplets and t heir signatures in relativistic heavy-ion collisions are discussed. [S0556- 2813(99)00406-9].