Charged hadron transverse momentum distributions in Au+Au collisions at   $\sqrt{s_{_{NN}}} =$ 200 GeV
  We present transverse momentum distributions of charged hadrons produced in Au+Au collisions at $\sqrt{s_{_{NN}}} =$ 200 GeV. The evolution of the spectra for transverse momenta $p_T$ from 0.25 to 5 GeV/C is studied as a function of collision centrality. We find a significant change of the spectral shape between proton-antiproton and peripheral Au+Au collisions. When comparing peripheral to central Au+Au collisions, we find that the yields at the highest $p_T$ exhibit approximate scaling with the number of participating nucleons, rather than scaling with the number of binary collisions. 
PHOBOS Collaboration: Gerrit J. van Nieuwenhuizen, et al