ar X iv : h ep - p h / 98 09 31 4 v 1 9 S ep 1 99 8 HIGH p T PHENOMENA IN HEAVY ION COLLISIONS AT √ s = 20 and 200 AGeV

Jet quenching as observed via high pT hadron production is studied in the HIJING1.35 model. We test the model on recent WA98 data on 160 AGeV Pb+ Pb → π up to 4 GeV/c. The results depend sensitively on the model of the Cronin effect. At (RHIC) collider energies ( √ s > 200 AGeV), on the other hand, semi-hard hadron production becomes insensitive to the above model and is thus expected to be a cleaner probe of jet quenching signature associated with non-Abelian radiative energy loss. WA98 Pb + Pb → π data [1] in the 2 GeV < p⊥ < 4 GeV range were analyzed recently by Wang [2] via a parton model. He showed that the parton model [3] is capable of reproducing the observed π invariant inclusive cross sections simultaneously in p + p, S + S [4], and central Pb + Pb [1] in the CERN/SPS energy range, √ s ∼ 20 AGeV. That analysis is interesting because it seems to imply the absence of quenching of high transverse momenta hadrons that should arise if partons lose energy in dense matter [5, 6]. The S+S and Pb+ Pb data clearly reveal, on the other hand, the expected Cronin enhancement [7] of moderate p⊥ pions, as seen first in p + A. The pp data confirm the need to supplement the LLA with non-perturbative intrinsic k⊥ [8, 9]. We address this problem here, following Ref. [10], using the HIJING event generator [11, 12]. ∗Talk given at the 8th Int. Workshop on Multiparticle Production, June 14-21, 1998, Mátraháza, Hungary