QGP formation and strange antibaryons

We analyze current experimental results and explore, as function of the collision energy and stopping in relativistic nuclear collisions, the production yields of strange antibaryons, assuming formation of a deconfined thermal QGP-fireball which undergoes a sudden hadronisation. PACS numbers: 25.75.+r, 12.38.Mh, 24.85.+p We present here a brief account of a study of the hadronic probes of quark-gluon plasma (QGP) involving in particular strange antibaryons. Hadronic particles can probe the QGP phase provided that there is rapid final state disintegration — in this case the abundances and spectra of hadrons reflect the conditions in the QGP [1, 2]. We assume thermalization of initially participating hadronic matter, and the formation in the collision at currently accessible energies √ s ≤ 10A GeV of a baryon-rich fireball in the central rapidity region. The latter hypothesis is inferred from the observed [3] rapidity distribution of Λ and Λ . These and other results show that the S–Ag/W/Pb and even the S–S collisions up to 200A GeV are very different from the ultra-relativistic limit [4], in which the valence quarks are expected to leave the central rapidity region. Furthermore, the anticipated [5] and experimentally confirmed [3, 6, 7] high production rate of (multiply) strange antibaryons in A–A reactions, and their central (in rapidity) spectral distributions are indicating a collective particle formation mechanism [8]: in the QGP reaction picture it is the ready made high density of (anti) strange quarks which leads under the rapid hadronisation scenario to high yields of (multiply) strange particles[5]. Particle yields from a rapidly dissociating fireball are proportional to the QGP particle fugacities λi, i = u, d, s: the fugacity of hadronic particles is the product of the valence quark fugacities, e.g. hyperons have the fugacity λY = λuλdλs. Because of u–d symmetry ∗Unité associée au CNRS UA 280.