Speaker
Description
We compute the single-spin asymmetry A_UL in semi-inclusive
deep-inelastic scattering of unpolarized leptons and longitudinally polarized
protons at large transverse momentum of the produced hadron. Our calculation is
performed in collinear factorization at the lowest order of QCD perturbation
theory. For photon exchange the asymmetry is T-odd and receives contributions
from the interference of the tree level and one-loop absorptive amplitudes. We
consider the behavior of the spin asymmetry at low transverse momentum where
contact to the formalism based on transverse-momentum dependent distribution
functions can be made. We also present some phenomenological results relevant
for the COMPASS and HERMES experiments and the future Electron-Ion Collider.
