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be masked by taking extreme energy loss extrapolations to $_{Lhc}$. However the double ratio R cb revealed very generic behavior, insensitive to the input parameters and radically different for the two coupling limits. Of crucial im- portance is the momentum range over which pQCD and AdS/CFT drag are self-consistent. Certainly pQCD must apply for p$_{T}$ → ∞ , but the scale below which nonperturbative effects become important is not yet well understood. Supposing that the AdS/CFT correspondence is relevant for heavy ion col- lisions, drag calculation momentum validity is limited from above. Since γ$_{c}$ depends on M$_{Q}$ but the hard pQCD scale does not there is likely a large re- 

