  Plans are underway to measure spin asymmetries at large momentum transfer in
hadron hadron collisions at RHIC and elsewhere. Proposals have focused on
measuring quark transversity and quark and gluon helicity distributions in the
nucleon. These experiments will also provide a strong and simple test of
perturbative QCD, namely that ${\cal A}_{TT}/{\cal A}_{LL}\ll 1$ in
$pp\rightarrow 2\, {\rm jets} +X$ and several related processes, whereas ${\cal
A}_{TT}/{\cal A}_{LL}\sim 1$ in Drell-Yan production of muon pairs. The
prediction tests the helicity, twist and chirality selection rules of
perturbative QCD that form the foundation for the analysis of spin dependent
hard processes. We estimate the ratio ${\cal A}_{TT}/{\cal A}_{LL}$ numerically
for polarized protons at RHIC.
