Understanding Jet Energy Loss with Angular Correlation Studies in PHENIX

Abstract

Angular correlation studies provide powerful insight into the energy loss of hard scattered partons as they traverse the partonic medium produced in heavy ion collisions at RHIC. These results are generally compared to jet correlations in p+p collsisions where all correlation strength is attributed to vacuum fragmentation. Strong modification to di-jet correlations has been observed in A+A collisions at RHIC, most notably for the away side jet. Many different effects, including the opacity of the medium, its response to energy deposited by partons as they propagate, and modifications to the parton fragmentation, are involved in producing the final correlation stuctures. Understanding the interplay between these various effects is essential to developing a complete picture of the medium. Measurements of jet correlations involving direct photons provide a unique probe of jet fragmentation effects, as photons are not strongly interacting. Additionally, systematic studies of the away side structure as a function of $p_{T}$, as well as attempts to include additional high $p_{T}$ trigger requirements, can help to distinguish different energy loss mechanisms. We discuss recent PHENIX results from these detailed studies of jet correlations in A+A and p+p collisions.