  We present an exploratory study of gaugino-pair production in polarized and
unpolarized hadron collisions, focusing on the correlation of beam polarization
and gaugino/Higgsino mixing in the general Minimal Supersymmetric Standard
Model. Helicity-dependent cross sections induced by neutral and charged
electroweak currents and squark exchanges are computed analytically in terms of
generalized charges, defined similarly for chargino-pair, neutralino-chargino
associated, and neutralino-pair production. Our results confirm and extend
those obtained previously for negligible Yukawa couplings and nonmixing
squarks. Assuming that the lightest chargino mass is known, we show numerically
that measurements of the longitudinal single-spin asymmetry at the existing
polarized pp collider RHIC and at possible polarization upgrades of the
Tevatron or the LHC would allow for a determination of the gaugino/Higgsino
fractions of charginos and neutralinos. The theoretical uncertainty coming from
factorization scale and squark mass variations and the expected experimental
error on the lightest chargino mass is generally smaller than the one induced
by the polarized parton densities, so that more information on the latter would
considerably improve on the analysis.
