Nuclear Physics Seminars

Transverse spin asymmetries that are observed in hadron production in DIS can be explained in the transverse-momentum-dependent (TMD) PDF approach as arising from correlations between the spin and the intrinsic transverse momentum of quarks and the spin of the parent nucleon.

These correlations should give rise to transverse spin asymmetries for example in the production of Drell-Yan muon pairs in the scattering of pi- off transversely polarized protons. The same effect could appear in J/psi production, though the magnitude depends on the production mechanism. COMPASS has collected data with pi- beam and transversely polarized NH3 target and the analysis of the J/psi production is in progress. The production of J/psi in muon-proton scattering on the other hand can proceed via the photon-gluon fusion process, gamma* g -> c cbar. Measurement of this process thus allows to access the gluon TMD PDFs. COMPASS has measured this process with transversely polarized proton target and the results will be presented.