Theory Forecast Joseph Kapusta University of Minnesota Sixty Years of Fireballs Joseph Kapusta University of Minnesota

Particle Production in High Energy Collisions is Mostly a Strong Coupling Problem in Quantum Field Theories This makes life difficult for theorists but it gives joy to experimentalists!

Gary D. Westfall b. June 10, 1950

Fermi proposed the following necessary conditions for the method to apply: 1. “…only states that are easily accessible from the initial state may actually attain statistical equilibrium…” 2.“…photons (which) could be created will certainly not have time to develop (statistical equilibrium)…” 3.“Notice the additional conservation law for the difference of the number of nucleons and anti-nucleons.” Fermi assumed a Lorentz contracted volume of overlapping projectile and target in the center of momentum frame, eventually found to be in disagreement with experiment.

Pomeranchuk argued that the reaction volume should expand to the point where particles would decouple from each other, given their inelastic reaction cross sections.

Statistical bootstrap model and/or data on hadronic mass spectrum Huang & Weinberg (1970) obtained the same result from the Veneziano model (1 st string theory).

Early 1970’s φ 3 multiperipheral model generalized multiperipheral model with clusters/fireballs

Bevatron built in 1954 to discover the antiproton.

Bevatron + SuperHILAC = Bevalac Purpose: Create dense nuclear matter in the laboratory for a brief moment : Beams of carbon and oxygen accelerated to 2.1 GeV/nucleon : Upgraded to accelerate beams up to uranium at 1 GeV/nucleon. 1993: Turned off for the last time, being eclipsed by the higher energies available at the AGS at BNL and at the SPS at CERN.

*This paper has been cited 408 times.

geometry kinematics thermodynamics

Introduction of the Pomeranchuk freeze-out and chemical potentials into the nuclear fireball model.

The fireball (or 2 fireball) model does not conserve angular momentum! The firestreak model does.

*This paper has been cited 216 times.

Probing Dense Nuclear Matter in the Laboratory Subal Das Gupta and Gary Wetfall Physics Today, May 1993

Many people have contributed to the interpretation of heavy ion data in terms of statistical models in the past thirty years including but not limited to: F. Becattini, P. Braun-Munzinger, J. Cleymans S. Das Gupta, M. Gazdzicki, U. Heinz, P. Huovinen J. Letessier, D. Magestro, A. Mekjian, J. Rafelski K. Redlich, H. Satz, J. Stachel, J. Sollfrank, N. Xu

Temperature Hadron ratios:

Compilation of freezeout conditions from the SIS, AGS, SPS and RHIC.

Long-Standing Question: How can thermalization be achieved (if indeed it is) on a time scale less than 1 fm/c?

3D viscous - smooth initial conditions 3D viscous - lumpy initial conditions McGill group

Happy Birthday to Gary and to fireballs! Supported by the Office Science, U.S. Department of Energy.