Hadron-hadron correlations at low and high p_T in heavy-ion collisions

The modification of two particle correlations within a jet due to its propagation through dense strongly interacting matter is explored. Different properties of the medium may be probed by varying the momentum of the detected hadrons. Very high transverse momentum ($p_T$) correlations sample the gluon density of the medium; the minimal modification on the same side as the trigger is consistent with the picture and parameters of partonic energy loss. Lower momentum hadrons, sensitive to the presence of composite structures in the medium may excite collective modes such as Cherenkov radiation, resulting in conical patterns in the detected correlations.