For heavy-ion collisions at the BNL Relativistic Heavy Ion Collider (RHIC) a scaling behavior is found in the dependencies on azimuthal angle ϕ and impact parameter b for pion production at high pT essentially independent of the hadronization process. The scaling variable is in terms of a dynamical path length ξ that takes into account detailed properties of geometry, medium density, and probability of hard scattering. It is shown in the recombination model how the nuclear modification factor depends on the average ξ̄(ϕ,b). The data for π...
