Evidence for an emission source of large space-time extent in Au+Au collisions at RHIC

The source imaging technique of Brown and Danielewicz has been used to extract two-pion emission source functions over a broad range of k _T and centralities in Au+Au collisions at $\sqrt s = 200$ GeV. The source functions reflect the combined contributions of a short-range Gaussian-like component and a long-range exponential-like component. A parametrization of the source function gives a RMS radius for the long-range source which is approximately three times that for the short-range source. The centrality dependence of the extracted source parameters for the short- and long-range sources indicate similar patterns.