Longitudinal density correlations of produced matter in Au+Au collisions at root s(NN)=200 GeV have been measured from the inclusive charged particle distributions as a function of pseudorapidity window sizes. The extracted alpha xi parameter, related to the susceptibility of the density fluctuations in the long-wavelength limit, exhibits a nonmonotonic behavior as a function of the number of participant nucleons, N-part. A local maximum is seen at N-part similar to 90, with corresponding energy density based on the Bjorken picture of epsilon(Bj)tau similar to 2.4 GeV/(fm(2)c) with a transverse area size of 60 fm(2). This behavior may suggest a critical phase boundary based on the Ginzburg-Landau framework.