  In R-parity conserving supersymmetric models, sleptons are produced in pairs
at hadron colliders. We show that measurements of the longitudinal single-spin
asymmetry at possible polarization upgrades of existing colliders allow for a
direct extraction of the slepton mixing angle. A calculation of the
transverse-momentum spectrum shows the importance of resummed contributions at
next-to-leading logarithmic accuracy in the small and intermediate
transverse-momentum regions and little dependence on unphysical scales and
non-perturbative contributions.
