  The higher order moments of the net-baryon distributions in relativistic
heavy ion collisions are useful probes for the QCD critical point and
fluctuations. We study the net-proton distributions and their moments in a
simple model which considers the baryon stopping and pair production effects in
the processes. It is shown that a single emission source model can explain the
experimental data well. Centrality and energy dependence of the distributions
and higher moments is discussed.
