Collins Effect from Polarized SIDIS and $e^+e^-$ Data

Abstract

The recent data on the transverse single spin asymmetry $A_{UT}^{\sin(\phi_h+\phi_S)}$ from HERMES and COMPASS Collaborations are analysed within LO parton model with unintegrated parton distribution and fragmentation functions. A fit of SIDIS data from HERMES Collaboration is performed leading to the extraction of favoured and unfavoured Collins fragmentation functions. A very good description of COMPASS data is obtained. BELLE $e^+e^-$ data are shown to be compatible with our estimates based on the extracted Collins fragmentation functions. Predictions for $A_{UT}^{\sin(\phi_h+\phi_S)}$ asymmetries at JLab and COMPASS operating on a proton target are given.