Jet quenching in high energy nuclear collisions and the quark-gluon plasma

We investigate the energy loss of quark and gluon jets in quark-gluon plasma produced in the central Au+Au collisions at RHIC energy. We use the physical characteristics of initial and mixed phases found in the effective quasiparticle model (Yu. A. Tarasov, hep-ph/0307300). We also take into account the possibility of hot glue production at the first stage. We calculate the suppression of {pi}{sup 0} spectrum, which is caused by the energy loss of gluon and quark jets. We compare this suppression with data reported by PHENIX. We find that the suppression is described correctly by the quasiparticle model with decrease of thermal gluon mass and effective coupling in the region of phase transition (at T{yields}T{sub c} from above). Thus it is possible to investigate the structure of phase transition with the help of hard processes. We also show, that the energy loss at SPS energy is too small to be observable. This is caused, in fact, by too low initial temperature of the plasma phase at this energy.