109 Chapter 4: Fluctuations in Jet Tomography R e AA < 0 . 5 without violating the bulk dN$_{g}$/dy = 1000 entropy constraint and without violating the pion quenching constraint R π 0 AA ≈ 0 . 2 ± 0 . 1 now observed out to 20 GeV; see Fig. 4.8. We note that the slow rise of R π 0 AA with p$_{T}$ in the present calculation is due in part to the neglect of initial k$_{T}$ smearing that raises the low p$_{T}$ region and the EMC effect that lowers the high p$_{T}$ region (see [277]). The ultimate goal of hard probe physics is jet tomography, the use of the high- p$_{T}$ hadronic attenuation pattern to learn about the medium density. One needs then a theoretical description of the processes involved that describes the data, has a mapping from its parameter(s) to the matter density, and is under calibrated control. For these tools to be truly tomographic, however, there is the additional re- quirement that the resulting medium measurement be reasonably precise. The overall precision of density determination is set by a combination of experimen- tal precision and theoretical sensitivity: if the experimental data are infinitely precise, any model with the previous paragraph’s characteristics could asses the medium density with similar precision; but experimental error exists and must be taken seriously, limiting the precision of medium determination by the innate sensitivity of the theoretical model to changes in its input parame- ter. Additionally there will also be theoretical error. Sources for this include, 4.5 Sensitivity and Imprecision in WHDG