Creation of strange-quark-matter droplets as a unique signature for quark-gluon plasma formation in relativistic heavy-ion collisions.

Abstract

We demonstrate that strangeness separates in the Gibbs-phase coexistence between a baryon-rich quark-gluon plasma and hadron matter, even at T=0. For finite temperatures this is due to the associated production of kaons (containing s\ifmmode\bar\else\textasciimacron\fi{} quarks) in the hadron phase while s quarks remain in the deconfined phase. The s-s\ifmmode\bar\else\textasciimacron\fi{} separation results in a strong enhancement of the s-quark abundance in the quark phase. This mechanism is further supported by cooling and net strangeness enrichment due to the prefreezeout evaporation of pions and ${K}^{+}$, ${K}^{0}$, which carry away entropy and anti- strangeness from the system. Metastable droplets (i.e., stable as far as weak interactions are not regarded) of strange-quark matter (``strangelets'') can thus be formed during the phase transition. Such cool, compact, long-lived clusters could be experimentally observed by their unusually small Z/A ratio (\ensuremath{\le}0.1--0.3). Even if the strange-quark-matter phase is not stable under strong interactions, it should be observable by the delayed correlated emission of several hyperons. This would serve as a unique signature for the transient formation of a quark-gluon plasma.