The energy and momentum lost by a hard parton propagating through hot and dense matter has to be redistributed in the nuclear medium. Apart from heating the medium, there is the possibility that collective modes are excited. We 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. Under the assumption that a sound wave is created, we track the jet energy loss as a function of spacetime and follow the resulting mach cone throughout the fireball evolution.We compare with the angular correlation pattern of hard hadrons as obtained by the PHENIX collaboration and find good agreement with the data provided that a substantial fraction of jet energy ($\sim$ 90%) is deposited into a propagating mode and that the hot matter can be characterized by an EOS with a soft point (not necessarily a mixed phase).Comment: 5 pages, 3 figures, submitted to PR

We perform a systematic comparison of three different jet energy-loss approaches. These include the Armesto-Salgado-Wiedemann scheme based on the approach of Baier-Dokshitzer-MuellerPeigne-Schiff and Zakharov (BDMPS-Z/ASW), the Higher Twist approach (HT) and a scheme based on the approach of Arnold-Moore-Yaffe (AMY). In this comparison, an identical medium evolution will be utilized for all three approaches: not only does this entail the use of the same realistic three-dimensional relativistic fluid dynamics (RFD) simulation, but also includes the use of identical initial parton-distribution functions and final fragmentation functions. We are, thus, in a unique position, not only to isolate fundamental differences between the various approaches, but also to make rigorous calculations for different experimental measurements using "state of the art" components. All three approaches are reduced to a version which contains only one free tunable parameter, this is then related to the well known transport parameterq. We find that the parameters of all three calculations can be adjusted to provide a good description of inclusive data on RAA versus transverse momentum. However, we do observe slight differences in their predictions for the centrality and azimuthal angular dependence of RAA vs. pT . We also note that the value of the transport coefficientq in the three approaches to describe the data differs significantly.

This writeup is a compilation of the predictions for the forthcoming Heavy Ion Program at the Large Hadron Collider, as presented at the CERN Theory Institute ‘Heavy Ion Collisions at the LHC—Last Call for Predictions’, held from 14th May to 10th June 2007.