Anomalous Anti-proton to Negative Pion Ratio as Revealed by Jet Quenching at RHIC

Abstract

We study the apparent discrepancy between the standard PQCD predictions for the meson and baryon ratios and multiplicities at moderate high $p_{T} > 2$ GeV and recent experimental measurements in $Au+Au$ collisions at $\sqrt{s}_{NN}=130$ GeV at the Relativistic Heavy Ion Collider (RHIC). We show that the differences, most pronounced in central collisions, can be explained by a strong non-perturbative baryon Junction component, which dominates the currently accessible experimental $p_{T}$ window and the non-abelian energy loss of fast partons propagating through hot and dense medium. The recently introduced two component hybrid model, which combines a quenched jet PQCD calculation in the Gyulassy-Levai-Vitev (GLV) formalism and a phenomenological "soft" part, is further elaborated to take into account the full 3D expansion in the pre-hadronization phase and include particle flavor dependent "soft" inverse slopes as suggested by the baryon Junction picture. We show that such approach can resolve what seems to be a factor of $\simeq 2$ difference in the moderate high $p_{T}$ suppression of $\pi^0$ and $h^-$ as recently reported by the PHENIX collaboration. The observed quenching of the high $p_{T}$ particle spectra and the large $\bar{p}/\pi^-$ and $p/\pi^+$ ratios as a function of $p_{T}$ are found to be consistent with a creation of a deconfined phase and non-abelian energy loss of fast partons in a plasma of initial gluon rapidity density $dN^g/dy \sim 1000$.