2 00 4 Radiative parton energy loss and jet quenching in high - energy heavy - ion collisions ∗ B . G . Zakharov

We study within the light-cone path integral approach [3] the effect of the induced gluon radiation on high-pT hadrons in high-energy heavy-ion collisions. The induced gluon spectrum is represented in a new form which is convenient for numerical simulations. For the first time, computations are performed with a realistic parametrization of the dipole cross section. The results are in reasonable agreement with suppression of high-pT hadrons in Au+ Au collisions at √ s = 200 GeV observed at RHIC. 1. One of the most interesting results obtained at RHIC is the suppression of high-pT hadrons in Au+Au collisions (for a review of the data, see [1]). It is widely believed that parton energy loss due to the induced gluon radiation caused by multiple scattering in the quark-gluon plasma (QGP) produced in the initial stage of nucleus-nucleus collisions plays a major role in this phenomenon (usually called jet quenching) [2, 3, 4, 5, 6, 7] (for a review, see [8]). The most general approach to the induced gluon emission is the light-cone path integral (LCPI) approach developed in [3] (see also [9, 10, 8]). It accurately treats the mass and finite-size effects, and applies at arbitrary strength of the Landau-Pomeranchuk-Migdal (LPM) effect [11, 12]. Other available approaches have limited domains of applicability, and can only be used either in the regime of strong (the BDMPS formalism [2, 5]) or weak (the GLV formalism [6]) LPM suppression (the GLV approach [6], in addition, is restricted to the emission of soft gluons). For this reason they can not be used for an accurate analysis of jet quenching for RHIC (and LHC) conditions. The LCPI approach expresses the gluon spectrum through the solution of a twodimensional Schrödinger equation with an imaginary potential in the impact parameter plane. The imaginary potential is proportional to the cross section of interaction of the q̄qg system (for q → gq transition) with a particle in the medium, σ3(ρ) (here ρ is the transverse distance between quark and gluon, the antiquark is located at the center of mass of the qg-system). The σ3(ρ) can be written as σ3(ρ) = C(ρ)ρ . The factor C(ρ) has a smooth (logarithmic) dependence on ρ for ρ ≪ 1/μD (hereafter, μD is the Debye ∗Supported by DFG-grant Schi 189/6-1