on $(\eta_1,\eta_2)$ and $(\phi_1,\phi_2)$ for the most central event class, denoted (a). Deviations from unity ($\hat r - 1$) of this [*per-pair*]{} correlation measure contain a [*dilution factor*]{} [@dilution] $1/\bar N$ ($\bar N$ is defined as the mean multiplicity in the detector acceptance) and are therefore numerically a few [*permil*]{} for central Au-Au collisions. However, the correlation structure is large compared to statistical errors ([*cf.*]{} Figs. \[Figure2\]-\[Figure4\]). A sinusoid associated with elliptic flow (consistent with conventional reaction-plane measurements) dominates the $(\phi_1,\phi_2)$ correlations in the right panel. The [*anti*]{}correlated LS distribution on $(\eta_1,\eta_2)$ in the left panel (anticorrelated: depression along the $\eta_1 = \eta_2$ diagonal) suggests charge ordering from longitudinal string fragmentation as in p-p collisions [@lund; @isrpp]. However, these correlations projected separately onto $(\eta_1,\eta_2)$ and $(\phi_1,\phi_2)$ are incomplete, and quite misleading for A-A collisions. A more complete picture is obtained from 2D [joint]{} autocorrelations on difference variables $(\eta_\Delta,\phi_\Delta)$ as shown in Fig. \[Figure2\].

![\[Figure2\] Perspective views of two-particle CD joint autocorrelations $\bar N (\hat r-1)$ on $(\eta_{\Delta},\phi_{\Delta})$ for central (a) to peripheral (d) collisions. Center bins at $\phi_{\Delta} = \eta_{\Delta} = 0$, containing photon-conversion electron pairs, were omitted from model fits.](cdfitaya1 "fig:"){width="1.65in"} ![\[Figure2\] Perspective views of two-particle CD joint autocorrelations 