  Differential measurements of various particle species over an extended
momentum range provide a sensitive experimental tool for investigation of
energy loss mechanisms in the medium created in nucleus-nucleus collisions at
RHIC. In these proceedings, a systematic study of transverse momentum spectra
for charged pions, protons and antiprotons from Cu+Cu data at
$\sqrt{s_{NN}}=200$GeV as a function of collision centrality will be presented.
Such systematic studies provide additional insights into the interplay between
fragmentation and non-fragmentation contributions to the particle production.
To investigate system size effects on energy loss, a comparison of top energy
results for Cu+Cu and Au+Au collision systems are made.
