but approximately double as $|\eta_{\Delta}|$ increases from 0 to 2 (due to finite $\eta$ acceptance). Statistical errors at $\eta_{\Delta} \sim 0$ vary from $\pm$0.00015 for central collisions to $\pm$0.0007 for peripheral collisions, again reflecting the $1/\bar N$ dilution factor. In contrast, statistical errors for $\bar N(\hat r - 1)$ in Fig. \[Figure2\] are approximately $\pm 0.2$ (one tick) for $\eta_\Delta \sim 0$ and are independent of centrality. Statistical errors for projections in Fig. \[Figure3\] are shown explicitly in that figure by error bars. Systematic errors were estimated as in [@meanptprl]. Systematic uncertainties associated with two-track inefficiency corrections and small momentum scale correlation cuts are negligible for this analysis. Systematic error due to non-primary backgrounds (dominant source) [@spectra], whose correlation with true primary particles is unknown, is estimated to be at most $\pm$7%, assumed uniform for all $(\eta_{\Delta},\phi_{\Delta})$ in the STAR acceptance. Contributions from resonance $(\rho^0 , \omega )$ decays are estimated to be at most about 10% of the negative peaks at $\phi_\Delta = \eta_\Delta = 0$ in Fig. \[Figure2\] in the range $|\eta_{\Delta}| < 0.5$, $|\phi_{\Delta}| < 2$ [@mevsim].

Model Fits
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The distributions in Fig. \[Figure2\] and their counterpart for p-p collisions [@jeffpp] reveal two asymptotic forms at 