Theory Forecast

Joseph KapustaUniversity of Minnesota

Sixty Years of Fireballs

Joseph KapustaUniversity 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. Westfallb. 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 expandto the point where particles would decouple from each other,given their inelastic reaction cross sections.

Statistical bootstrap model and/ordata on hadronic mass spectrum

0

exp~T

MM

dM

dN a

re temperatulimiting a is MeV 160 Inferred 0 T

Huang & Weinberg (1970) obtained the sameresult from the Veneziano model (1st string theory).

Early 1970’s

φ3 multiperipheral model generalized multiperipheral model with clusters/fireballs

pppppp

Bevatron built in 1954 to discover the antiproton.

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.

*This paper has been cited 408 times.

geometrykinematicsthermodynamics

Introduction of thePomeranchuk freeze-outand chemical potentialsinto the nuclear fireballmodel.

The fireball (or 2 fireball) model does not conserveangular 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. CleymansS. Das Gupta, M. Gazdzicki, U. Heinz, P. HuovinenJ. Letessier, D. Magestro, A. Mekjian, J. RafelskiK. Redlich, H. Satz, J. Stachel, J. Sollfrank, N. Xu

Temperature

• Hadron ratios:2

( ) /20

( , )2 1i i s ii

ii E B S TT

g p dpn

e

Compilation of freezeout conditionsfrom 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 initialconditions

3D viscous -lumpy initialconditions

McGill group

Happy Birthday to Gary and to fireballs!

Supported by the Office Science, U.S. Department of Energy.