Hard probes in heavy-ion collisions

• High pT (jets, prompt g) & large mass (D, B, J/Y) particles.

• Early production (t~1/pT~ 0.1 fm/c) in parton-parton scatterings with large Q2

• Direct probes of partonic phases Þ Sensitive to hot/dense medium (QGP) effects: energy loss, color screening.

• Comparison to available set of baseline "vacuum" data (pp Ö AA) via Ncoll (# of binary inelastic colls.) scaling:

• Elementary processes calculable via pQCD. Factorization theorem: