Subleading-twist effects in single-spin asymmetries in semi-inclusive deep-inelastic scattering on a longitudinally polarized hydrogen target

Single-spin asymmetries in the semi-inclusive production of charged pions in deep-inelastic scattering from transversely and longitudinally polarized proton targets are combined to evaluate the subleading-twist contribution to the longitudinal case. This contribution is significantly positive for π+ mesons and dominates the asymmetries on a longitudinally polarized target previously measured by Hermes. The subleading-twist contribution for π− mesons is found to be small.