195 Appendix B: Power Law R$_{AA}$ power law, where A is some normalization constant, then we may find a simple equation for the partonic nuclear modification factor, dN q prod dp$_{i}$ ( p$_{i}$ ) = A p n ( p$_{i}$ ) i , (B.8) R q $_{AA}$( p$_{T}$ ) ≡ dN q AA dp$_{T}$ ( p$_{T}$ ) N$_{coll}$ dN q pp dp$_{T}$ ( p$_{T}$ ) (B.9) = N$_{coll}$ ∫ dϵ dN q prod dp$_{i}$ ( p$_{T}$ 1 − ϵ ) 1 1 − $_{ϵ}$P ( ϵ | p$_{T}$ 1 − $_{ϵ}$) N$_{coll}$ dN q prod dp$_{T}$ ( p$_{T}$ ) = N$_{coll}$ ∫ dϵ A ( p$_{T}$ / 1 − ϵ ) n ( p T / 1 − ϵ ) 1 1 − $_{ϵ}$P ( ϵ | p$_{T}$ 1 − $_{ϵ}$) N$_{coll}$ A p n ( p T ) T = ∫ dϵP ( ϵ | p$_{T}$ 1 − ϵ )(1 − ϵ ) n ( p$_{T}$ / 1 − ϵ ) − 1 p n ( p$_{T}$ ) T p n ( p$_{T}$ / 1 − ϵ ) T . (B.10) R q $_{AA}$( p$_{T}$ ) ≃ ∫ dϵP ( ϵ )(1 − ϵ ) n ( p$_{T}$ ) − $^{1}$. (B.11) In the case of a slowly varying power law n ( p$_{T}$ ) is approximately independent of p$_{T}$ ; if we further assume a slow variation of P with respect to p$_{T}$ we have We note that if the production spectra are dN q $_{prod}$/d$^{2}$p$_{T}$ or dN q $_{prod}$/dp 2 T then the exponent in Eq. (B.11) goes from n ( p$_{T}$ ) − 1 to n ( p$_{T}$ ) − 2.