Probing Hot, Dense Matter at Rhic

Recent experimental data indicate the appearance of jet-quenching effect in central Au+Au collisions at RHIC. Jet energy loss is able to measure the density of colored particles in the interaction zone. We apply the GLV theory of QCD radiative energy loss to estimate the opacity, L/λ_g, of the produced gluon plasma. We show that the data can be accounted for with an effective static plasma opacity L/λ_g ≈ 3-4.