First-Order Chiral Phase Transition May Naturally Lead to a “Quenched” Initial Condition and Strong Soft-Pion Fields

Abstract

We propose a novel mechanism for disoriented chiral condensate (DCC) formation in a first-order chiral phase transition. In this case the effective potential for the chiral order parameter has a local minimum at $\ensuremath{\Phi}\ensuremath{\sim}0$ in which the chiral field can be ``trapped.'' If the expansion is fast, a bubble of disoriented chiral field can emerge and decouple from the rest of the fireball. The bubble may overshoot the mixed phase and supercool until the barrier disappears, when the potential resembles that at $T\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0$. This situation corresponds to the initial condition realized in a ``quench.'' Thus, the subsequent alignment in the vacuum direction leads to strong amplification of low-momentum modes of the pion field. We propose that these DCCs could accompany the previously suggested baryon rapidity fluctuations.