Separation in number of standard deviations ($S_\sigma$) as a function of momentum between: pions and protons (upper panels), pions and kaons (middle panels), and kaons and protons (lower panels). Results are shown for 0-5% (left panels) and 40-60% (middle panels) $\pbpb$; and pp (right panels) collisions. Because the TPC response is track-length dependent, the separation is better for tracks at forward pseudorapidities (solid lines) than for those at smaller $\eta$ (dashed lines). The degradation in separation power in more central collisions is expected from occupancy effects - in the most peripheral collisions an average of $149$ clusters are assigned to tracks with $\pt > 2\gevc$, while in the most central collisions only $127$ clusters are assigned.