The Mini-Jet Scale and Energy Loss at RHIC in the HIJING and RQMD Models

Abstract

The original default mini-jet scale p_0=2 GeV/c and energy loss, dE/dx=2 GeV/fm in HIJING lead to a too rapid growth of the multiplicity with energy. RQMD model without mini-jet leads on the other hand to a too slowly increasing multiplicity with energy. We show that a slight increase of p_0 from the default 2.0 GeV/c at sqrt(s)=130A GeV to 2.2 GeV/c at sqrt{s}=200A GeV is sufficient to account for the bulk observables. Jet quenching of pi^0 above p_T>4 GeV/c at 200A GeV is found to be well reproduced in central Au+Au by the original HIJING default prediction. However, the effective surface emission in the HIJING model formulation of energy loss over-predicts the quenching in more peripheral collisions. Neither HIJING nor HIJING/B{bar}B can account for the observed anomalous excess of moderate p_T<4 GeV/c baryons. The agreement of RQMD with data in this p_T region is shown to be fortuitous because, without mini-jets, it fails to reproduce the p+p spectrum.

36 pages,Latex(revtex), 13 figures, submitted to Phys. Rev. C