Contribution of Vector Meson Dominance to the Single-Spin Azimuthal Asymmetry in Semi-inclusive Pion Electro-Production

We calculate the contribution of vector meson dominance to deeply inelastic lepton-nucleon scattering in the kinematic region of the HERMES experiment. The results obtained show that this contribution is quite significant. Together with the fact that there exist very striking left-right asymmetries for hadron produced in single-spin hadron-hadron collisions, these results imply that the single-spin azimuthal asymmetry observed by HERMES cannot be simply regarded as a pure fragmentation effect.