Thermal Hadron Production by QCD Hawking Radiation

The QCD counterpart of Hawking radiation from black holes leads to thermal hadron production in high energy collisions, from $e^+e^-$ annihilation to heavy ion interactions. This hadronic radiation is formed by tunnelling through the event horizon of colour confinement and is emitted at a universal temperature $T_H \simeq (\sigma /2 \pi)^{1/2}$, where $\sigma$ denotes the string tension. Since the event horizon does not allow information transfer, the radiation is thermal ``at birth''.Comment: 17 pages, 12 figures; updated version of an invited talk at the workshop "Critical Point and Onset of Deconfinement", Firenze/Italy, July 3-6, 200

Charm and Beauty in a Hot Environment

We discuss the spectral analysis of quarkonium states in a hot medium of deconfined quarks and gluons, and we show that such an analysis provides a way to determine the thermal properties of the quark-gluon plasma.Comment: 14 pages, 15 figures; presented at the meeting "A Sense of Beauty in Physics", honoring the 70th birthday of Adriano Di Giacomo; Pisa, Jan. 26 -27, 200

Quarkonium Binding and Entropic Force

A Q-Qbar bound state represents a balance between repulsive kinetic and attractive potential energy. In a hot quark-gluon plasma, the interaction potential experiences medium effects. Color screening modifies the attractive binding force between the quarks, while the increase of entropy with Q-Qbar separation gives rise to a growing repulsion. We study the role of these phenomena for in-medium Q-Qbar binding and dissociation. It is found that the relevant potential for Q-Qbar binding is the free energy F; with increasing Q-Qbar separation, further binding through the internal energy U is compensated by repulsive entropic effects.Comment: 11 pages, 8 figure

A Brief History of J/Psi Suppression

Statistical QCD predicts that strongly interacting matter will become deconfined at high temperatures and/or densities. The aim of high energy nuclear collisions is to study the onset of deconfinement and the properties of deconfined media in the laboratory. Hence it is essential to define an unambiguous and experimentally viable probe for deconfinement. Twelve years ago, T. Matsui and I proposed that \J~production should constitute such a probe \cite{M&S}, and I want to sketch here rather briefly the evolution of this idea in the light of subsequent experimental and theoretical work.Comment: 7 pages, latex, two figures (included

QCD & QGP: A Summary

Contents: 1. The Thermodynamics of Quarks and Gluons 2. Hard Probes: Colour Deconfinement 3. Electromagnetic Probes: Chiral Symmetry Restoration 4. Soft Probes: Equilibration and Expansion 5. ConclusionsComment: 20 pages, Latex; Theory Summary, International Conference on the Physics and Astrophysics of the Quark-Gluon Plasma (ICPA-QGP'97), Jaipur/India, March 15 - 21, 199

Colour deconfinement in hot and dense matter

We first introduce the conceptual basis of critical behaviour in strongly interacting matter, with colour deconfinement as QCD analog of the insulator-conductor transition and chiral symmetry restoration as special case of the associated shift in the mass of the constituents. Next we summarize quark-gluon plasma formation in finite temperature lattice QCD. We consider the underlying symmetries and their spontaneous breaking/restoration in the transition, as well as the resulting changes in thermodynamic behaviour. Finally, we turn to the experimental study of strongly interacting matter by high energy nuclear collisions, using charmonium production to probe the confinement status of the produced primordial medium. Recent results from Pb-Pb collisions at CERN may provide first evidence for colour deconfinement.Comment: 11 pages tex, uses macro-hs.tex, 10 figures; talk given at CRIS '96, First Catania Relativistic Ion Studies, Acicastello, Italy, May 27 - 31, 1996; to appear in the Proceeding

Color Deconfinement and Charmonium Production in Nuclear Collisions

In statistical QCD, color deconfinement and the properties of the quark-gluon plasma determine the in-medium behavior of heavy quark bound states. In high energy nuclear collisions, charmonia probe the partonic medium produced in the early stages of the interaction. We survey the present theoretical status and provide a critical evaluation of the charmonium production measurements in experiments at the CERN-SPS and the BNL-RHIC.Comment: 62 pages, 86 figure

The States of Matter in QCD

Quantum chromodynamics predicts that the interaction between its fundamental constituents, quarks and gluons, can lead to different states of strongly interacting matter, dependent on its temperature and baryon density. We first survey the possible states of matter in QCD and discuss the transition from a color-confining hadronic phase to a plasma of deconfined colored quarks and gluons. Next, we summarize the results from non-perturbative studies of QCD at finite temperature and baryon density, and address the origin of deconfinement in the different regimes. Finally, we consider possible probes to test the basic features of bulk matter in QCD.Comment: 31 pages, 24 figure