Medium modification of jet fragmentation in Au+Au collisions at √sNN=200 GeV measured in direct photon-hadron correlations

The jet fragmentation functionis measured with direct photon- hadroncorrelations in p + p and Au + Au collisions at root S-NN = 200 GeV. The P-T of the photon is an excellent approximation to the initial P-T of the jet and the ratio Z(T) = P-T(h)/P-T(gamma) is used as a proxy for the jet fragmentation function. A statistical subtraction is used to extract the direct photon- hadronyields in Au + Au collisions while a photon isolation cut is applied in p + p. I-AA, the ratio of hadronyield opposite the photon in Au + Au to that in p + p, indicates modification of the jet fragmentation function. Suppression, most likely due to energy loss in the medium, is seen at high Z(T). The associated hadronyield at low Z(T) is enhanced at large angles. Such a trend is expected from redistribution of the lost energy into increased production of low-momentum particles.