content_image/297605.jpg content_image/297606.jpg
observable difference between the mass and p$_{T}$ dependencies of the AdS/CFT drag and pQCD-inspired energy loss models. One can see in Fig. 5.3 that not only are most overall normalization differences canceled, but also that the curves remarkably bunch to either AdS/CFT-like or pQCD-like generic results regardless of the input parameters used. 

The numerical value of R cb shown in Fig. 5.3 for AdS/CFT can be roughly understood analytically from Eq. (5.5) as, 

<img src='content_image/297605.jpg'>

where in this approximation all λ , T $^{∗}$, L , and n$_{c}$ ( p$_{T}$ ) ≈ n$_{b}$ ( p$_{T}$ ) dependences drop out. 

The pQCD trend in Fig. 5.3 can be understood qualitatively from the expected behavior of ¯ ϵ$_{pQCD}$ noted above giving (with n$_{c}$ ≈ n$_{b}$ = n ) 

<img src='content_image/297606.jpg'>

where p$_{cb}$ = κn ( p$_{T}$ ) L $^{2}$log( M$_{b}$/M$_{c}$ )ˆ q sets the relevant momentum scale. Thus R cb → 1 more slowly for higher opacity. One can see this behavior reflected in the full numerical results shown in Fig. 5.3 for moderate suppression, but that the extreme opacity ˆ q = 100 case deviates from Eq. (5.7). 

Supposing that Lhc data are similar to the pQCD predictions one might be able to distinguish between convolved elastic and inelastic loss, for which R cb monotonically increases, and purely radiative energy loss, for which R cb 

