Twist-3 single-spin asymmetries in semi-inclusive deep-inelastic scattering
Institut für Theoretische Physik II, Ruhr-Universität Bochum, D-44780 Bochum, Germany
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Accepted: 19 July 2004
Published online: 11 November 2004
The single-spin asymmetries for a longitudinally polarized lepton beam or a longitudinally polarized nucleon target in semi-inclusive deep-inelastic scattering are twist-3 observables. We study these asymmetries in a simple diquark spectator model of the nucleon. Analogous to the case of transverse target polarization, non-vanishing asymmetries are generated by gluon exchange between the struck quark and the target system. It is pointed out that the coupling of the virtual photon to the diquark is needed in order to preserve electromagnetic gauge invariance at the twist-3 level. The calculation indicates that previous analyses of these observables are incomplete.
PACS: 13.60.Hb Total and inclusive cross-sections (including deep-inelastic processes) – / 13.88.+e Polarization in interactions and scattering –
© Società Italiana di Fisica and Springer-Verlag, 2004