  We consider the leading twist $T$-odd contributions as the dominant source of
the $\cos 2\phi$ azimuthal asymmetry in unpolarized $p\bar{p}\to \mu\mu^+ X$
dilepton production in Drell-Yan Scattering. This asymmetry contains
information on the distribution of quark transverse spin in an unpolarized
proton. In a parton-spectator framework we estimate these asymmetries at $50
{\rm GeV}$ center of mass energy. This azimuthal asymmetry is interesting in
light of proposed experiments at GSI, where an anti-proton beam is ideal for
studying the transversity properties of quarks due to the dominance of {\em
valence} quark effects.
