$\eta$-distributions at 130 GeV and 200 GeV with various centrality cuts have been analyzed by means of a stochastic model, i.e., the Ornstein- Uhlenbeck process. To improve previous description utilized in Prog. Theor. Phys. 108 (2002)559, 109(2003)151 and 109(2003)483, we propose a model with three sources at two nuclei $\pm y$ and the central region ($y\approx 0$). Comparisons of our results and those based on QCD are made.