New picture of jet quenching

We have released a paper to the arxiv in which a new picture of jet quenching dictated by color coherent parton branching is presented. The paper can be find at

The description of the parton shower of jets in the presence of a medium is one of the main goals of the HotLHC project. Following the philosophy of the vacuum studies, we are performing analytical calculations in limiting cases where controlled calculations are possible to acquire a better and better understanding of the whole problem. One of the essential ingredients is color coherence. The effect of color coherence among different emitters in the medium have been studied in a series of papers in the setup known as the antenna radiation. Based on this knowledge, we propose a new picture in which the jet is composed by a reduced number of effective emitters. Each of this effective emitter is an extended object, with typical size determined by the medium color correlation length, inside which regular vacuum branching can appear. 

Two main consequences of the appearance of color coherence are a reduced energy loss, due to a reduced number of effective emitters, and an unmodified fragmentation functions for each emitter. 

This new picture provides a consistent understanding of the present data on reconstructed jet observables and constitute the basis for future developments. 

In order to check the relevance of this effect to the actual LHC kinematics we have made a proof-of-principle study reclustering the reconstructed jets from a Monte Carlo event generator with the typical medium characteristic angular scale. We find that at least one-half of the jets measured at the LHC may be unresolved by the medium, hence composed of only one effective emitter.