Transversity and Collins Fragmentation Functions: Towards a New Global Analysis

Understand

A new, preliminary global analysis of the experimental data on azimuthal asymmetries in SIDIS from HERMES and COMPASS collaborations, and in e+e- --> h_1 h_2 X processes from the BELLE collaboration, is performed.

• The new data allow for a more precise determination of the Collins fragmentation function and of the transversity distribution function for $u$ and $d$ quarks, in comparison with the results of our previous analysis.
• Estimates for the single spin asymmetry A_UT^{\sin(\phi_h + \phi_S)} at JLab and COMPASS, operating on a transversely polarized proton target, are presented.