Transverse momentum dependent distribution function h1Tperpendicular and the single spin asymmetry AUTsin(3φ-3S)

The leading twist transverse momentum dependent parton distribution function h1Tperpendicular is studied. We review the theoretical properties of this function, and compute it in the bag model. We find in the bag model an interesting relation, and observe it to hold also in other relativistic models: The difference between helicity and transversity distributions, often said to be a 'measure of relativistic effects' in the nucleon, is related to h1Tperpendicular. This function is chirally odd and can be accessed in combination with the Collins effect in semi-inclusive deep-inelastic scattering, where it gives rise to an azimuthal single spin asymmetry proportional to sin(3φ-φS). We discuss preliminary COMPASS data on that observable and make predictions for future experiments on various targets at JLab, COMPASS, and HERMES.