Download WestFest: Sixty Years of Fireballs

Sixty Years of Fireballs
Theory Forecast
Joseph Kapusta
Joseph
Kapusta
University of Minnesota
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
M
dN
a
~ M exp 
dM
 T0



Inferred T0  160 MeV is a limiting temperatu re
Huang & Weinberg (1970) obtained the same
result from the Veneziano model (1st string theory).
Early 1970’s
φ3 multiperipheral model
generalized multiperipheral
model with clusters/fireballs
Bevatron built in 1954 to discover the antiproton.
p p p p p p
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.
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:

gi
p 2 dp
ni (T ,  )  2  ( Ei  i Bi  s Si ) / T
2 0 e
1
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.