40 Chapter 2: Motivation more on this later. [306] was the first to coin the term ‘fragility,’ which we will take to mean the limit on information about the medium that can be learned by inverting the experimental data with theoretical modeling. The paper raised the issues of surface emission, sensitivity, and fragility, and used these terms rather in- terchangeably. In this thesis each term has a separate meaning and will be addressed individually. As noted before the production of high- p$_{T}$ partons is biased toward the center of a heavy ion collision because the process scales like the number of binary collisions. Due to the large background of low- p$_{T}$ particles full jet reconstruction algorithms are not yet available for $_{Rhic}$, although both Star and Phenix are actively researching them [307–309]. Limited to measuring the leading hadron of a jet, experimental cuts combined with the in-medium energy loss and steeply-falling production spectra bias the production point of observed high- p$_{T}$ particles toward the surface of the medium; see Fig. 2.8. Na¨ıvely one expects that there will always be a corona of emission, or surface emission: near the very edge of the fireball the medium is so thin high- p$_{T}$ partons escape with little or no energy loss. This naturally leads to the idea of a minimum nuclear modification value, R min $_{AA}$, below which jets cannot be further suppressed. In fact this is not a correct conclusion for systems with realistic nuclear densities because at the outer edge of the medium no hard scatterings occur: the thinness of the nuclear overlap results in no binary collisions. In fact Section 5.2 explicitly shows R$_{AA}$ → 0 for large energy loss.