From Mach Cone to Reappeared Jet: What Do We Learn from PHENIX Results on Non-Identified Jet Correlation?

Jet properties, extracted from two particle azimuth correlation, are found to be strongly modified in Au + Au collisions at √s_NN = 200 GeV. At intermediate p_T and in central Au + Au collisions, the modifications appear as a broadening of jet width at the near side and a cone structure at the away side. As one increase the p_T for both hadrons, the away side cone structure seems to gradually evolve into a peak structure. The interpretation of these results requires careful separation of various medium effects and surface bias.