  For high energy nucleus-nucleus collisions, we show that a combination of
space-momentum correlations characteristic of radial expansion together with
the correlation between the position of a nucleon in the nucleus and its
stopping, results in a very specific rapidity dependence of directed flow: a
reversal of sign in the mid-rapidity region. We support our argument by RQMD
model calculations for Au+Au collisions at $\sqrt s$ = 200 AGeV.
