Accessing TMDs at HERMES

Transverse Momentum Dependent (TMD) parton distribution functions are being recognized as crucial ingredients for a complete understanding of the nucleon structure. Describing correlations between the quark or the nucleon spin with the quark transverse momentum, they allow for a tridimensional description of the nucleon structure in momentum space and could provide insights into the yet unmeasured quark orbital angular momentum. Eight leading-twist TMDs contribute to the cross-section for lepton-hadron Semi Inclusive Deep Inelastic Scattering (SIDIS) in conjunction with a fragmentation function. At HERMES, TMDs are probed for various hadron types through the analysis of specific azimuthal modulations of the SIDIS cross-section. Three double-spin asymmetries sensitive to the TMD (worm-gear) g ⊥ 1T, recently extracted from data collected with a transversely polarized target and a longitudinally polarized beam, are reported. © 2012 American Institute of Physics