Three-particle azimuthal correlations and Mach shocks

Measurements of angular correlations of hadrons with a (semi-)hard trigger hadron in heavyion collisions at RHIC show large angular structures opposite to the trigger which were a priori unexpected. These away side large angle correlations were first observed in two-particle correlations [1, 2] and have recently also been investigated in three-particle correlation measurements [3, 4]. We show that the correlation signal can be understood in terms of sonic shockwaves (’Mach cones’) excited by hard partons supersonically traversing the medium. The propagation of such shocks through the medium evolution is treated in a Monte Carlo (MC) framework [6, 7]. We demonstrate that twoand especially three-particle correlations offer non-trivial insight into the medium-averaged speed of sound and the evolution of flow. Our findings imply that the assumption of ”deflected jets” is not necessary to account for the observed correlations.