the centrality limits: a 1D gaussian on $\eta_\Delta$ ([*uniform*]{} on $\phi_\Delta$) for p-p collisions and a 2D exponential on $(\eta_\Delta,\phi_\Delta)$ for central Au-Au collisions. The two forms may be limiting cases of a single evolving structure, or they may correspond to two independent correlation mechanisms with complementary centrality trends. A preliminary fitting exercise indicated that these 130 GeV Au-Au data do not have sufficient statistical power or centrality range to explore the possibility of a single evolving peak structure. We therefore used the simpler superposition model.

The distributions in Fig. \[Figure2\] were fitted with a five-parameter model function consisting of a 2D exponential function peaked on both $\eta_{\Delta}$ and $\phi_{\Delta}$ and a 1D gaussian on $\eta_{\Delta}$, constant on $\phi_\Delta$ (the latter motivated by the p-p limiting case [@isrpp; @jeffpp]) plus a constant offset, all defined relative to quantity $\hat r - 1$ as \[Eq3\] F & = & A\_0 + A\_1 { -\^ }\
& + & A\_2 {-( )\^2 }  . $F$ interpolates between the 1D gaussian peak observed in p-p and the 2D exponential peak observed in central Au-Au collisions. Correlations between amplitudes $A_1$ and $A_2$ were negligible because of the distinct one- and two-dimensional peak shapes. Parameters 