hadron talk - ISR freezeout parameters

NIX-CHAPMAN FREEZEOUT PARAMETERS FOR THE NA44 DATA SET - PRELIMINARY

After feeding the model all the NA44 singles and pairs data, it settles at a chisquare minimum with parameter values as shown in the table below. One of the beauties of the model is that it produces error bars. This allows us to see how well a data set can constrain a particular parameter (even if you disagree with this particular implementation).

parameter	value and uncertainty at 99% confidence

Nuclear temperature T	102 +- 25 MeV
Baryon chemical potential mu-b/T	4.3 +- 2.3
Pion incoherence fraction lambda-pi	1.0 (fixed)
Transverse freezeout radius R	10.8 +- 2.5
Transverse freezeout velocity v-t	0.67 +- 0.09 c
Transverse freezeout coefficient alpha-t	0 (fixed)
Source rapidity y	2.92 +- 0.066
Longitudinal spacetime rapidity eta-0	3.9 +- 2.2
Longitudinal freezeout proper time tau-f	9.9 +- 3.8 fm/c

Again, the temperature seems low in light of the 140 or so MeV temperature derived from the systematics of hadron slopes, as shown on preceeding slides (#4,5), but it is similar to the AGS value.
for this fit, I fixed the pion BE lambda to 1.0, on the conviction that the lambda we observe is entirely due to resonance decays, which are already in the model.
The parameter alpha, which determines if the freezeout occurs from the outside in (-1) or from the inside out (+1) was fixed at 0.

Reference: Phys.Rev. C54 (1996) 866, or a copy on the web

HvH, Phenix hadron workshop, March '97, Costa mesa

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