  Direct photon-hadron correlations are a golden channel to study parton
in-medium energy loss in QGP. The modification of the effective fragmentation
function for the away-side jet can be measured by comparing integrated
away-side yields of direct photon-hadron pairs in heavy ion collisions to those
in p+p. We measured per-trigger-yield of associated hadrons in Au+Au collisions
and observed that there is a suppression compared to p+p for higher momentum
fraction ($z_T$) hadrons. This can be explained by the opacity of the hot
medium: energetic partons from the initial hard scattering lose energy while
traversing it. A yield enhancement on the other hand has been found at low
$z_T$ (high $\xi$). Medium response is likely to be responsible for the
enhanced production of these lower momentum particles. The same measurement is
done in d+Au collisions and the result suggests that no modification to the
fragmentation function is observed, given the current uncertainties.
