Exclusive Hadronic Reactions at High $Q^2$ ($90\degree$) and Polarization Phenomena, An Experimental Proposal}

Arguments are presented for the expected behaviour of $\piNpiN$ scattering and the $\pbarppipi$ reaction at high energy and large scattering angles. % The annihilation reaction has close to maximal asymmetry ($\approx$ 1) for $p_{lab} \siml$ 2.2 GeV/c. % As will be presented for fixed (90$\degree$) angle this large asymmetry will not become zero but will start to oscillate with energy at higher energies and large $Q^2$ when perturbative QCD becomes applicable. This is due to the energy dependence of a QCD phase difference between the independent quark-quark scattering (Landshoff) and short-distance processes at high but not asymptotic energies. % A consequence of the existence the Landshoff process is that even if helicity is conserved at the quark level ($m_{q}$ = 0 MeV), helicity does not have to be conserved on the hadronic level. % We will discuss the implications for spin observables in $pp$ elastic scattering and argue that