Two-particle Direct Photon-Jet Correlation Measurements in PHENIX

Various 2-particle direct photon-hadron correlation yields in p + p and Au + Au collisions at √ sNN = 200 GeV are presented. The per-trigger yield of direct photon hadron pairs from direct-photon-jet correlations is obtained by a statistical subtraction of the decay photon pairs from inclusive photon-hadron sample. The decay photon pertrigger yields are estimated from the measured π-hadron by means of a Monte Carlo based calculation which takes into account decay kinematics and detector response. Under the assumption that the suppression is nearly pT independent using a specific averaging scheme, we find a ratio of Au + Au to p + p per-trigger photon yields IAA averaged over all available pT bins consistent with the single particle suppression level RAA, which can be interpreted as a qualitative confirmation of the basic geometrical picture of jet suppression at RHIC. The application of the event by event photon isolation cuts in p + p results our highest precision measurement yet, and allows for precision studies of the baseline fragmentation function D(z) and also a determination of the apparent intrinsic kT , or non-zero transverse momentum of the original collision partons. With a model dependent extraction method, the average √ < k T > at this √ s in p+ p is found to be approximately 2.5-3 GeV, consistent with analysis of di-hadron (di-jet) correlations [1]. Finally, we present a unique direct measurement of prompt photons from jet fragmentation.