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Explore the history and advancements in the study of fireballs in high energy collisions. From Fermi's necessary conditions to statistical models and dense nuclear matter, this paper delves into the complex world of particle production.
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Sixty Years of Fireballs Theory Forecast Joseph Kapusta University of Minnesota 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: • “…only states that are easily accessible from the initial • state may actually attain statistical equilibrium…” • “…photons (which) could be created will certainly not • have time to develop (statistical equilibrium)…” • “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 (1st string theory).
Early 1970’s generalized multiperipheral model with clusters/fireballs φ3 multiperipheral model
Bevatron + SuperHILAC = Bevalac Purpose: Create dense nuclear matter in the laboratory for a brief moment. • 1974-75: Beams of carbon and oxygen accelerated to 2.1 GeV/nucleon. • 1981-82: 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.
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.
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 McGill group 3D viscous - lumpy initial conditions
Happy Birthday to Gary and to fireballs! Supported by the Office Science, U.S. Department of Energy.