Intriguing Centrality Dependence of the Au-Au Source Size at the AGS

Abstract

One of the main goals of high energy heavy ion physics is to establish the existence of a deconfined phase of nuclear matter — the quark-gluon plasma — at high temperatures or densities. One possible signature of such a phase transition, especially if it were first order, would be a larger source size or lifetime than a similar hadronic system. At current AGS energies, we attempt to form a quark-gluon plasma by achieving a high baryon density for a period of time in the center of the collision regioni^[1]. For a given density threshold, the size of this high density region should be a strong function of the impact parameter: the more central the event, the larger the high density region. Therefore, one possible signature of a quark-gluon plasma would be a sudden change in system lifetime or size as a function of the centrality of the collision.