Searching for the Next Yukawa Phase of QCD

QCD predicts that the interactions between quarks and gluons change from a confining to a screened Yukawa form above a critical temperature $T_c\sim 150$ MeV. In this talk, I review some of the key observables in heavy ion reactions which are being used to search for this new partonic Yukawa phase at SPS and RHIC. These include collective observables such as $dE_\perp/dyd^2p_\perp$, meson interferometry, jet quenching, and $J/\psi$ suppression.Comment: 24 pages (PTPTex style files included) with 26 eps,ps figures using epsf,psfig. To appear in Proc. of 14th Nishinomiya-Yukawa Memorial Symposium Nov. 1999, Japan; updated with a critique of the CERN press release Feb. 8, 200

The Next Yukawa Phase of QCD at RHIC

QCD predicts the existence of a new partonic Yukawa phase above a critical temperature $T_c\sim 150$ MeV. I review some of the key observables which will be used in heavy ion reactions to search for this new phase at RHIC. Systematics of collective observables ($N_{ch},E_\perp)$, flow patterns, meson interferometry, jet quenching, and $J/\psi$ suppression are discussed. This talk is updated with the first data from RHIC.Comment: 18 pages, including 18 figures. Invited talk given at the 7th International Conference on Nucleus-Nucleus Collisions (NN2000), Strasbourg, 3-7 July 2000, to appear in the Proceedings in Nucl. Phys. A (W. Noerenberg, D. Guerreau, and V. Metag, editors

The Transverse Energy as a Barometer of a Saturated Plasma

The evolution of the gluon plasma produced with saturation initial conditions is calculated via Boltzmann transport theory for nuclear collisions at high energy. The saturation scale increases with the nuclear size and the beam energy, and thus we find that the perturbative rescattering rate decreases relative to the initial longitudinal expansion rate of the plasma. The effective longitudinal pressure remains significantly below the lattice QCD pressure until the plasma cools to near the confinement scale. Therefore, the transverse energy per unit of rapidity and its dependence on beam energy provides a sensitive test of gluon saturation models: the fractional transverse energy loss due to final state interactions is smaller and exhibits a weaker energy dependence than if ideal (nondissipative) hydrodynamics applied throughout the evolution.Comment: 4 Pages, LaTex, 2 Figures; Contribution to the 15th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions (QM 2001), Long Island, New York, January 15 - 20, 200