  We present first results of azimuthal (Delta phi) correlations of high
transverse momentum (p_T) hadrons from the high-statistics Au+Au dataset
collected at RHIC in 2004. Previous correlations measurements observed the
disappearance of back-to-back (Delta phi ~ pi) correlations in central Au+Au
collisions, supporting the emerging picture of parton energy loss in dense QCD
matter. In the present analysis, increasing the p_T thresholds reveals a narrow
back-to-back dijet peak which emerges above the decreasing combinatoric
background. We study the possible medium modification of the dijet
fragmentation function and compare to models, to place constraints on the
nature and magnitude of in-medium energy loss.
