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(-) --> h(1) h(2) 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)(S)(sin(phi)+phi(h)), as will soon be measured at JLab and COMPASS operating on a transversely polarized proton target, are then presented.
Transversity and Collins functions from SIDIS and e(+)e(-) data
D'ALESIO, UMBERTO;
2007-01-01
Abstract
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(-) --> h(1) h(2) 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)(S)(sin(phi)+phi(h)), as will soon be measured at JLab and COMPASS operating on a transversely polarized proton target, are then presented.
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