For Au Au collisions at 200 GeV, we measure neutral pion production with good statistics for transverse momentum, p(T), up to 20 GeV/c. A fivefold suppression is found, which is essentially constant for 5 { p(T) { 20 GeV/c.
Experimental uncertainties are small enough to constrain any model-dependent parametrization for the transport coefficient of the medium, e. g., {(q) over cap } in the parton quenching model. The spectral shape is similar for all collision classes, and the suppression does not saturate in Au Au collisions.