Analysis of the d/p Ratios in Au + Au Collisions AT 11.1 GeV/c

Abstract

The most interesting aspect of high energy heavy-ion collisions is that they provide the opportunity to produce matter at high net baryon density. In particular, under these conditions a signature of the quark-gluon plasma (QGP) formation may be found[1]. Beam energies of around 10 GeV per nucleon seem to achieve the stopping of two colliding nuclei creating a high density matter region[2, 3]. It is important to look for experimental probes that allow the study of the properties of this region, such as lifetime, volume, entropy, etc. Deuteron production by phase space coalescence is interesting because it can be used to study the space-time structure of the participant zone[4]. Once the participant region is formed in a heavy-ion collision, the baryon density increases up to a maximum, followed by a radial expansion of nuclear matter. At some point in this expansion (freeze-out time), composite particles are formed by coalescence. Since a proton and neutron form a deuteron when their relative momentum in phase space is small[6], the deuteron production is a measure of the source baryon density and/or the extension of the freeze-out zone[7]. Furthermore, a strong first-order QGP with a large latent heat may expand before hadronization so that the baryons would be formed at a lower density. Hence, suppression in the deuteron formation may be an indication of plasma formation[8].