Single transverse-spin asymmetry in semi-inclusive deep inelastic scattering

We study the single transverse-spin asymmetry in semi-inclusive hadron production in deep inelastic scattering. We derive the leading contribution to the asymmetry at moderate transverse momentum Ph⊥ of the produced hadron in terms of twist-three quark–gluon correlation functions, and compare with the result obtained from the approach based on factorization at fixed transverse momentum which involves asymmetric transverse-momentum and spin-dependent quark distributions. We verify that the two approaches yield identical results in this regime. Comparing with our earlier calculations for the single-spin asymmetry in the Drell–Yan process, we confirm the sign difference between the time-reversal-odd transverse-momentum-dependent quark distributions in the two processes.