The origin of large-pT π0 suppression at RHIC

We present results for inclusive two production in proton-proton and in Au-Au at RHIC energy rootS = 200 GeV. We use next-to-leading order perturbative QCD calculation and we include nuclear effects such as parton energy loss and nuclear shadowing. We consider the ratio of pi(0) distribution in Au-Au and p-p collisions for PT > 3 GeV for three cases of parton energy loss: (1) constant parton energy loss per parton scattering, is an element of(n)(a) = const, (2) Landau-Pomeranchuk-Migdal energy-dependent energy n loss, is an element of(n)(a) similar to rootE(n)(a) and (3) Bethe-Heitler energy-dependent energy loss, is an element of(n)(a) similar to is an element of(n)(a). We show that recently observed suppression of pi(0) production in Au-Au collisions at RHIC, which is found to increase with PT increasing from 3 GeV to 8 GeV, can be reproduced by is an element of(n)(a) = 0.06E(n)(a). We show that the ratio of prompt photons to neutral pions produced in Au-Au collisions at RHIC has a strong PT dependence approaching one at PT - 10 GeV. (C) 2003 Published by Elsevier Science B.V.