Strangeness and thresholds of phase changes in relativistic heavy ion collisions

We discuss how the dynamics of the evolving hot fireball of quark--gluon matter impacts phase transition between the deconfined and confined state of matter. The rapid expansion of the fireball of deconfined matter created in heavy ion collisions facilitates formation of an over-saturated strange quark phase space. The related excess abundance of strangeness is compensating the suppression of this semi-heavy quark yield by its quark mass. In addition, the dynamical expansion of colored quanta pushes against the vacuum structure, with a resulting supercooling of the transition temperature. We address the status of the search for the phase boundary as function of reaction energy and collision centrality and show evidence for a change in reaction mechanism at sufficiently low energies. The phase diagram derived from the study of hadron production conditions shows two boundaries, one corresponding to the expected transition between confined and deconfined matter, with a downward temperature shift, and the other a high quark density hadronization which appears to involve heavy effective quarks, at relatively large temperatures.Comment: 10 Pages, presented at Workshop on Light-Cone QCD and Nonperturbative Hadron Physics 2005 (LC2005), Cairns, July 2005, to appear in proceeding

Strange Antibaryons from QGP

We study as function of the collision energy and stopping the thermal conditions reached in a quark-gluon plasma fireball formed in a relativistic heavy ion collision. We explore strange particle yields for the current round of Pb-Pb and Au-Au experiments.Comment: 4 pages, LaTeX, 3 postscript figures, Presented at Quark Matter 1995, Montere

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.Comment: Replaced by the published version. 11 pages, 3 figure

Auger : A Large Air Shower Array and Neutrino Telescope

Detection of Ultra High Energy Neutrinos (UHEN), with energy above 0.l EeV (10**18 eV) is one of the most exciting challenges of high energy astrophysics and particle physics. In this article we show that the Auger Observatories, built to study ultra high energy cosmic rays, are one of the most sensitive neutrino telescopes that will be available in the next decade. Furthermore, we point out that the Waxman-Bahcall upper bound for high energy neutrino fluxes below 1 EeV turns into a lower bound above a few EeV. In this framework and given the experimental evidences for nu_mu nu_tau oscillations with large mixing, we conclude that observation of Tau UHEN in the southern Auger Observatory should most certainly occur within the next five years.Comment: 6 pages, 6 figures, 1 table. Talk given at the neutrino 2002 conference. To be published in Nuclear Physics B (Proceedings Supplement) Corrected misplaced WB limit in Figure

Centrality Dependence of Bulk Fireball Properties at RHIC

We explore the centrality dependence of properties of the dense hadronic matter created in \sqrt{s_{NN}}=200 GeV Au--Au collisions at RHIC. Using the statistical hadronization model we fit particle yields known for 11 centrality bins. We present the resulting model parameters, rapidity yields of physical quantities and the physical properties of bulk matter at hadronization as function of centrality. We discuss the production of strangeness and entropy.Comment: 7 pages including 5 figures, 1 table: more information provided: figure 1 in lieu of work in progress defines phi-data, table for statistical parameters for all models as function of centrality, additional references and reference update, section captions, PRC `nearly to be published'.... look out for further updates, referees run amoc

Neutrinos and the Highest Energy Cosmic Rays

Observation of Ultra High Energy Cosmic Rays (UHECR) -whose energy exceeds $10^20$eV- is still a puzzle for modern astrophysics. The transfer of more than 16 Joules to a microscopic particle can hardly be achieved, even in the most powerful cosmic accelerators such as AGN's, GRB's or FR-II radio galaxy lobes. Potential sources must also lie within 100 Mpc of the Earth as the interaction length of protons, nuclei or photons is less than 10Mpc. However no visible counterpart of those sources has been observed. Calling upon new physics such as Topological Defect interactions or Super Massive Relic Particle decays is therefore very tempting, but such objects are yet to be proven to exist. Due to the very low flux of UHECR only very large dedicated experiments, such as the Auger observatories, will allow to shed some light on the origin of those cosmic rays. In this quest neutrinos, if they can be detected, are an invaluable messengers of the nature of the sources.Comment: Talk Given at the Neutrino 2000 COnference. Sudbury, Toronto June 12-17 2000 7 pages, 8 figure

Non-equilibrium Hadrochemistry in QGP Hadronization

This survey offers an introductory tutorial for students of any age of the currently thriving field of hadrochemistry. We discuss the different chemical potentials, how the hadronic phase space is described and how one evaluates the abundance of hadrons at time of hadronization. We show that a rather accurate description of experimental data arises and we present results of fits to hadron yields at SPS and RHIC. We show that introduction of chemical non-equilibrium originating in a sudden hadronization of a QGP is favored strongly at SPS and is presently also emerging at RHIC. The low chemical freeze-out temperatures are consistent with the picture of single freeze-out scenario (chemical and thermal freeze-out coincide).Comment: To appear in the proceedings of Pan American Advanced Studies Institute on New States of Matter in Hadronic Interactions (PASI 2002), Campos do Jordao, Brazil, 7-18 Jan 2002; American Institute of Physics 2002 *v2 Contains UPDATED RHIC-130 chemical freeze-out analysis

Strangeness and Statistical Hadronization: How to Study Quark-Gluon Plasma

Statistical hadronization is presented as mechanism for (strange) particle production from a deconfined quark--gluon plasma (QGP) fireball. We first consider hadronic resonance production at RHIC as a test of the model. We present in detail how the hadrochemistry determines particle multiplicities and in case of sudden hadronization allows investigation of QGP properties. A comparative study of strange hadron production at SPS and RHIC is presented. The energy dependence of physical observables shows regularities and a potential discontinuity in the low RHIC range, when comparing these different energy domains. Considering the energy scan program at CERN-SPS we show that the K^+/\pi^+ discontinuity is a baryon density effect.Comment: 35 pages, 15 figures, presented at the Cracow School of Theoretical Physics, Zakopane, May 30 - June 8, 200

Hadronization of Expanding QGP

We discuss how the dynamics of an exploding hot fireball of quark--gluon matter impacts the actual phase transition conditions between the deconfined and confined state of matter. We survey the chemical conditions prevailing at hadronization.Comment: 8 pages, presented at QGPTH05, Vienna, August 200

Strangeness and Statistical QCD

We discuss properties of statistical QCD relevant in Fermi phase space model analysis of strange hadron production experimental data. We argue that the analysis results interpreted using established statistical QCD properties are demonstrating formation of the color deconfined state of matter in relativistic heavy ion collisions at highest CERN-SPS energies and at BNL-RHIC, comprising deconfined matter composed of nearly massless quarks and gluons, in statistical equilibrium.Comment: 22 pages, including 7 figures, 3 tables, to appear in Nuclear Physics Proceedings Supplement: STATISTICAL QCD, held at Bielefeld August 200