Possibility of forming a large DCC in ultra-relativistic heavy-ion collisions

We demonstrate the possibility of forming a single, large domain of disorie nted chiral condensate (DCC) in a heavy-ion collision. In our scenario, rap id initial heating of the parton system provides a driving force for the ch iral field, moving it away from the true vacuum and forcing it to go to the opposite point on the vacuum manifold. This converts the entire hot region into a single DCC domain. Subsequent rolling down of the chiral field to i ts true vacuum will then lead to emission of a large number of (approximate ly) coherent pions. The requirement of suppression of thermal fluctuations to maintain the (approximate) coherence of such a large DCC domain, favors three-dimensional expansion of the plasma over the longitudinal expansion e ven at very early stages of evolution. This also constrains the maximum tem perature of the system to lie within a window. We roughly estimate this win dow to be about 200-400 MeV. These results lead us to predict that extremel y high energy collisions of very small nuclei (possibly hadrons) are better suited for observing signatures of a large DCC. Another possibility is to focus on peripheral collisions of heavy nuclei.