A global analysis of the experimental data on azimuthal asymmetries in semi-inclusive deep inelastic scattering (SIDIS), from the HERMES and COMPASS Collaborations, and in e+e- --> h1 h2 X processes, from the BELLE Collaboration, is performed. It results in the extraction of the Collins fragmentation function and, for the first time, of the transversity distribution function for u and d quarks. These turn out to have opposite signs and to be sizably smaller than their positivity bounds. Predictions for the azimuthal asymmetry A_{UT}^{sin(phi_h + phi_S)}, as will soon be measured at JLab and COMPASS operating on a transversely polarized proton target, are then presented.
@article{arxiv.hep-ph/0701006,
title = {Transversity and Collins functions from SIDIS and e+e- data},
author = {M. Anselmino and M. Boglione and U. D'Alesio and A. Kotzinian and F. Murgia and A. Prokudin and C. Turk},
journal= {arXiv preprint arXiv:hep-ph/0701006},
year = {2010}
}
Comments
Revised version to appear in Phys. Rev. D. Few misprints corrected, new figures