  PHENIX has measured the two particle azimuth correlation in Au + Au at
$\sqrt{s}$ = 200 GeV. Jet shape and yield at the away side are found to be
strongly modified at intermediate and low $p_T$, and the modifications vary
dramatically with $p_T$ and centrality. At high $p_T$, away side jet peak
reappears but the yield is suppressed. We discuss the possible physics pictures
leading to these complicated modifications.
