122 Chapter 5: pQCD vs. AdS/CFT Q 2 s ∼ Q 2 $_{0}$log( A √ s/p$_{T}$ ), that defines a scale below which strong initial state nuclear modification of the parton distributions must be taken into account, and ˆ qL ≡ ∫ dzdσρ ( z ) q 2 ∝ Q 2 s log $^{n}$( Q$_{s}$ ), below which strong final state nuclear modifications must be taken into account. For finite A < 238 and finite √ s < 10 ATeV the numerical values of these scales remains uncertain. Second is to suggest this observable will discriminate between current pQCD and AdS/CFT dynamical models. We start with the predicted nuclear modification, R Q $_{AA}$( p$_{T}$ ), of the trans- verse momentum distribution of identified heavy quark jets produced in central Pb+Pb reactions at 5.5 ATeV at$_{Lhc}$. Specifically, we propose that the double ratio of identified charm and bottom jet nuclear modification factors R c $_{AA}$/R b AA is a remarkably robust observable that can distinguish between a rather wide class of pQCD energy loss mechanisms and a recently proposed class of grav- ity “drag” models [336, 342, 343, 347, 434] of heavy quark dynamics. Similar tests can be performed at Rhic when identified jet flavor detector upgrades are completed. The main advantage of $_{Lhc}$in comparison to$_{Rhic}$ is of course the much higher p$_{T}$ kinematical range that will be accessible. The main advan- tage of Rhic is a better control of the initial state saturation physics because of extensive d + A and p + p control data at the same √ s . The current failure of pQCD based energy loss models [152, 298, 374, 435] to account quantitatively for the recent$_{Rhic}$ data from STAR [423] and$_{Phenix}$ [237, 424] on the nonphotonic electron spectrum provides additional moti- vation to focus on heavy quark jet observables. Unlike for light quark and