Signatures of Mach shocks at RHIC

Thorsten Renk

Hard partons propagating through hot and dense matter loose energy, leading to the observed depletion of hard hadron spectra in A-A collision as compared to scaled N-N collisions. This lost energy has to reappear in the medium due to the conservation of energy. Apart from heating the medium, there is the possibility that some propagating collective mode is excited. I outline a formalism that can be used to track the propagation of such a mode through the evolving medium if its dispersion relation is known and to calculate the resulting distortion of hadronic spectra at freeze-out. Using this formalism, I demonstrate within a detailed picture of the evolution of the expanding system and the experimental trigger conditions that the assumption of a sound mode being excited is in line with hard 2-particle correlation measurements at PHENIX and STAR. In this case, the data are sensitive to the averaged speed of sound in the hot matter. I also discuss the role of 3-particle correlation mesurements and alternative pictures to explain the data.