High-pT @ RHIC: theory confronting data

APPROACH “A” (pQCD + parton energy loss):
- Step 1: pQCD (NLO or LO+K-factor) = PDFs + scatt. matrix + FFs
- Step 2: pQCD + nPDF (shadowing) + pT broadening (Cronin)
- Peripheral data explained
Step 3: pQCD + initial-state nuclear effects + parton energy loss
- Energy loss 1: BDMPS, Wiedemann & Salgado (LPM, thick plasma)
- Energy loss 2: Gyulassy-Levai-Vitev (LPM, thin plasma)
- Energy loss 3: HSW (modified FFs), (g radiation + absorption)

Goal: explain central colls. (quenching, pT dependence, away-side suppr.)

Step 4: pQCD + IS nuc. effects + energy loss + parton recombination

Goal: explain baryon-meson diff. (Rcp, v2 ) in central colls.

APPROACH “B” (“classical” QCD):

Step 1: CGC → gluon saturated nuclear wave function (MLV) + geometric scaling (KLN)
Step 2: glue + glue collisions: gg  g
Step 3: Gluon fragmentation (FFs)

Goal: explain high pT deficit, away-side suppression, Npart scaling ...