Au+Au Global Results 2: Particle Multiplicity vs. centrality [PRL 86, 3500 (2001), and QM2002]

• dNch/dy (per participant pair) increases faster than linearly with centrality:

• dNch/dy constraints mechanisms of initial multi-particle production:

  •  "Soft + hard" (HIJING, pQCD “minijet”): increased hard contribution (Ncoll )
  •  Initial-state gluon saturation (CGC): dNch/dy ~ dNgluon/dy ~ 1/as ~ NpartlnNpart
  •  Final-state gluon saturation (EKRT)

Notes: