Photon-hadron jet correlations in p plus p and Au plus Au collisions at s(NN)=200 GeV (Article No. 024908)
Abstract
We report the observation at of suppression of back-to-back correlations in the direct photon jet channel in Au Au relative to p p collisions. Two-particle correlations of direct photon triggers with associated hadrons are obtained by statistical subtraction of the decay photon-hadron background.
The away-side nuclear suppression factor, I-AA, in central Au Au collisions, is 0.32 /- 0.12(stat) /- 0.09(syst) for hadrons of 3 { p(T)(h){ 5 in coincidence with photons of 5 { p(T)(gamma){ 15 GeV/c. The suppression is comparable to that observed for high-p(T) single hadrons and dihadrons.
The direct photon associated yields in p p collisions scale approximately with the momentum balance, z(T)equivalent to p(T)(h)/p(T)(gamma), as expected for a measurement of the away-side parton fragmentation function. We compare to Au Au collisions for which the momentum balance dependence of the nuclear modification should be sensitive to the path-length dependence of parton energy loss.