Time evolution of the chiral phase transition during a spherical expansion
- Department of Physics, University of New Hampshire, Durham, New Hampshire 03824 (United States)
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
We examine the nonequilibrium time evolution of the hadronic plasma produced in a relativistic heavy ion collision, assuming a spherical expansion into the vacuum. We study the O(4) linear {sigma} model to leading order in a large-{ital N} expansion. Starting at a temperature above the phase transition, the system expands and cools, finally settling into the broken symmetry vacuum state. We consider the proper time evolution of the effective pion mass, the order parameter {l_angle}{sigma}{r_angle}, and the particle number distribution. We examine several different initial conditions and look for instabilities (exponentially growing long wavelength modes) which can lead to the formation of disoriented chiral condensates (DCC{close_quote}s). We find that instabilities exist for proper times which are less than 3 fm/{ital c}. We also show that an experimental signature of domain growth is an increase in the low momentum spectrum of outgoing pions when compared to an expansion in thermal equilibrium. In comparison to particle production during a longitudinal expansion, we find that in a spherical expansion the system reaches the {open_quote}{open_quote}out{close_quote}{close_quote} regime much faster and more particles get produced. However the size of the unstable region, which is related to the domain size of DCC{close_quote}s, is not enhanced. {copyright} {ital 1996 The American Physical Society.}
- OSTI ID:
- 286431
- Journal Information:
- Physical Review, D, Journal Name: Physical Review, D Journal Issue: 3 Vol. 54; ISSN PRVDAQ; ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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