Mainz 2012 – scientific programme
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HK: Fachverband Physik der Hadronen und Kerne
HK 21: Schwerionenkollisionen und QCD Phasen
HK 21.9: Talk
Tuesday, March 20, 2012, 18:45–19:00, P 5
Thermalized or not thermalized? The SHM at SIS energies. — •Manuel Lorenz1, Romain Holzmann2, and Joachim Stroth1,2 — 1Goethe -Universität, Frankfurt — 2GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt
With the HADES detector we have investigated in great detail the collision system Ar+KCl at 1.76 AGeV. From the data, the up to now most complete set of particle species in the 1-2A GeV energy regime could be reconstructed. This allows for a stringent test of various phenomenological models, in particular statistical hadronization models. SHM have indeed been successful in extracting the freeze-out line in the T – µb plane of the nuclear phase diagram by fitting particle yields from relativistic and ultrarelativistic heavy ion collisions [1]. At energies of a few GeV, however, the validity of these models is not so well established, since it remains unclear whether chemical equilibrium can be reached, and therefore the question arises whether a statistical treatment of particle production is at all meaningful. The situation is further complicated by the need for strangeness suppression, which is handled differently in the various implementations of the SHM.
In this contribution, we compare the measured particle yields to an SHM fit and discuss the results critically with respect to the various signatures of thermalization of the collision system, in particular the strong deviation observed for double strange particles.
This work has been supported by BMBF (06 FY 9100 I), HIC for FAIR, EMMI and GSI.
A. Andronic, P. Braun-Munzinger and J. Stachel, Nucl. Phys. A 772, (2006) 167.