Speaker
Description
Within the QCD parton model approach, the quark structure of the polarized nucleon can be parametrized in terms of spin and quark transverse momentum dependent parton distribution functions while the hadronization mechanism is described by fragmentation functions. Specific convolutions of these objects can be accessed through the measurement of longitudinal spin-dependent asymmetries in semi-inclusive DIS processes. For this purpose COMPASS has performed a series of SIDIS measurements using 160-200 GeV/c polarized muons scattering off longitudinally polarized deuteron ($^{6}LiD$) and proton ($NH_3$) targets. In addition to already published single charged hadron production deuteron azimuthal asymmetries, COMPASS has recently extracted the whole set of proton asymmetries in this channel, as well as the asymmetries in di-hadon production. In this talk selected COMPASS results will be presented along with former results obtained by other collaborations and relevant theoretical model predictions.
