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Session A14 - Relativistic Heavy Ions I.
MIXED session, Thursday morning, May 02
Room 117,
We examine the time evolution of the hadronic plasma produced in an relativistic heavy ion collision, assuming a spherical expansion. We study the O linear sigma model to leading order in a large N expansion. We introduce the fluid variables ``proper time'' \tau = \sqrtt^2 - r^2 and radial fluid rapidity \eta = \tanh^-1(r/t). Starting at a temperature above the phase transition, we choose appropriate initial conditions and allow the system to expand and cool. We consider the proper time evolution of the effective pion mass, the order parameter \langle \sigma \rangle, 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. We find that instabilities exist for proper times approximately 3 fm/c. We also show that an experimental signature of domain growth is an increase in the low momentum spectrum when compared to an expansion in thermal equilibrium.