  The large single spin asymmetries observed at high momentum fractions x_F and
transverse momenta k_T in p^\uparrow p -> \pi(x_F,k_T)+X as well as in pp ->
\Lambda^\uparrow(x_F,k_T)+X suggest that soft helicity flip processes are
coherent with hard scattering. Such coherence can be maintained if x_F -> 1 as
k_T -> \infty, while k_T^2(1-x_F) \sim \Lambda_QCD^2 stays fixed. The entire
hadron wave function, rather than a single quark, then contributes to the
scattering process. Analogous coherence effects have been seen experimentally
in the Drell-Yan process at high x_F. We find that the p^\uparrow p ->
\pi(x_F,k_T)+X production amplitudes have large dynamic phases and that
helicity flip contributions are unsuppressed in this limit, giving rise to
potentially large single spin asymmetries.
