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HK: Hadronen und Kerne
HK 12: Heavy Ion Reactions II, Ultrarelativistic Energies
HK 12.5: Vortrag
Montag, 16. März 1998, 18:30–18:45, P
Dissipation and Fluctuation at the Chiral Phase Transition — •Carsten Greiner1, Tamas Biro2, and Zhe Xu1 — 1Institut für Theoretische Physik, Universität Giessen — 2MTA KFKI RMKI Theory Division, Budapest, Hungary
Utilizing the Langevin equation for the linear σ-model we investigate the interplay of friction and white noise on the evolution and stability of collective pionic fields in energetic heavy ion collisions. We find that the smaller the volume, the more stable transverse (pionic) fluctuations become on a homogeneous disoriented chiral field background (the average transverse mass ⟨ mt2⟩ increases). On the other hand the variance of mt2 increases even more, so for a system thermalized in an initial volume of 10 fm3 about 96 % and even in 1000 fm3 about 60 % of the individual trajectories enter into unstable regions (mt2 < 0) for a while during a rapid one dimensional expansion (τ0=1 fm/c). In contrast the ensemble averaged solution in this case remains stable. This result supports the idea of looking for disoriented chiral condensate (DCC) formation in individual events.
Supported by BMBF, DFG and the Hungarian Academy of Sciences