22 Chapter 2: Motivation duction rates [148–151] held out the possibility for jet tomography: much like in medical applications such as a Pet scan, a careful measurement of the jet quenching pattern would reveal information on the medium through which the probe traveled. As high transverse momentum parton jets are produced early in the collision (by Heisenberg’s Uncertainty Principle) and preferentially deep within the fireball—more on this later—they are potentially excellent probes of the medium. Naturally then before investing the tremendous time and resources nec- essary to investigate high- p$_{T}$ particles theoretically and experimentally, one should ruminate on the epistemology of hard probes. There were claims in [77] that jet suppression can merely give information on the density of scat- tering centers. This is an important measurement, as noted previously a high density is a prerequisite for QGP formation, but jets have the potential to in fact reveal much more than simply a mean density. The possibility of testing, e.g. deconfinement, depends heavily on the energy loss model and the mapping made between its input parameters and the physical medium. This mapping is a critical, although often overlooked, component of any model attempting tomography. As an example, the WHDG model [152] (see Chapter 4) explic- itly assumes a connection between the medium density, its temperature, and its Debye mass: light quarks and gluons are taken to have masses proportional to µ$_{D}$ , and the energy loss results are surprisingly sensitive to its changes; the elastic energy loss is derived from classical considerations that assume plasma polarization. Additionally Chapter 3 argues from a phenomenological ap-