"Conventional" nuclear effects (2): Gluon shadowing

• Relevant x region for high-pT (2-5 GeV/c) at RHIC:

• xT = 2pTparton/ Ös = 2 (pThadron/z) / Ös Þ

• [taking z~1, x~xT] Þ x ~ 0.03-0.08

• For x < 0.1: P(arton)DFs » G(luon)DFs:

• Specially true for nuclei:

• xG(x,Q2) ~ A1/3/xd (with d ~ 0.2-0.3)

• For x<0.1 : Nuclear PDFs depleted compared to proton PDFs

• R(x,Q2,A) º fiA(x,Q2) / [A fiN(x,Q2)] < 1 Ô Shadowing (parton recombination, ...)