  We study single spin asymmetries at one-loop accuracy in semi-inclusive DIS
with a transversely polarized hadron in the initial state. Two measurable spin
observables are predicted in the framework of QCD collinear factorization. One
of the spin observables is the Sivers weighted asymmetry, another one is the
Collins weighted asymmetry. The prediction takes a form of convolutions of
perturbative coefficient functions and nonperturbative functions, which are
twist-2 transversity distributions, twist-3 parton distributions, twist-2- and
twist-3 parton fragmentation functions. These nonperturbative functions can be
extracted from measurements of the spin observables and provide valuable
information of the inner structure of hadrons. The measurements can be done in
current COMPASS- and JLab experiments and in future experiments of EIC. The
perturbative coefficient functions are calculated at one-loop level. There are
collinear divergences in the calculation involving chirality-even- and
chirality-odd twist operators. We find that all collinear divergences can be
correctly subtracted so that the final results are finite.
