103 Chapter 4: Fluctuations in Jet Tomography Figure 4.5: Partonic nuclear modification, R II $_{Q}$( p$_{T}$ ) via Eq.(4.7), for g, u, c, b as a function of p$_{T}$ for fixed L=5 fm path length and dN$_{g}$/dy = 1000 . Dashed curves include only radiative energy loss, while solid curves include elastic energy loss as well. of surviving jets defined by ρ$_{Q}$ is given by the initial transverse ⃗ x production distribution times the quench- ing factor from that position in direction φ with final momentum p$_{T}$ . The case shown is for a p$_{T}$ = 15 GeV jet produced initially at ( x, 0) and moving in the direction φ = 0 along the positive x axis. The quenching is determined by the participant bulk matter along its path ρ$_{QGP}$ ( x + vt, 0 , t ), and varies with x because the local path length L = L ( x, 0 , 0) changes according to Eq. (4.3). ρ$_{Q}$ ( ⃗ x, φ ) ≡ ρ$_{Jet}$ ( ⃗ x )$^{∫}$ dϵ (1 − ϵ ) $^{n}$P I $_{Q}$( ϵ ; L ( ⃗ x, φ )) . (4.8)