  We study the single transverse-spin asymmetry for dijet production in
hadronic collisions in both the collinear QCD factorization approach and the
Brodsky-Hwang-Schmidt model. We show that a nonvanishing asymmetry is generated
by both initial-state and final-state interactions, and that the final-state
interactions dominate. We find that in the leading kinematic region where the
transverse momentum imbalance of the two jets, q_\perp = P_{1\perp}+P_{2\perp},
is much less than the momentum of either jet, the contribution from the lowest
non-trivial perturbative order to both the spin-averaged and the spin-dependent
dijet cross sections can be factorized into a hard part that is a function only
of the averaged jet momentum P_\perp = (P_{1\perp}-P_{2\perp})/2, and
perturbatively generated transverse momentum dependent (TMD) parton
distributions. We show that the spin asymmetry at this non-trivial perturbative
order can be described by the TMD parton distributions defined in either
semi-inclusive DIS or the Drell-Yan process. We derive the same hard parts from
both the collinear factorization approach and in the context of the
Brodsky-Hwang-Schmidt model, verifying that they are not sensitive to details
of the factorized long distance physics.
