Extracting the Sivers function from polarized SIDIS data and making predictions

M. Anselmino; M. Boglione; U. D'Alesio; A. Kotzinian; F. Murgia; A. Prokudin

Paper

Extracting the Sivers function from polarized SIDIS data and making predictions

Abstract

The most recent data on the weighted transverse single spin asymmetry

from HERMES and COMPASS collaborations are analysed within LO parton model with unintegrated parton distribution and fragmentation functions; all transverse motions are taken into account, with exact kinematics, in the elementary interactions. The overall quality of the data is such that, for the first time, a rather well constrained extraction of the Sivers function for

and

quarks is possible and is performed. Comparisons with models are made. Based on the extracted Sivers functions, predictions for

asymmetries at JLab are given; suggestions for further measurements at COMPASS, with a transversely polarized hydrogen target and selecting favourable kinematical ranges, are discussed. Predictions are also presented for Single Spin Asymmetries (SSA) in Drell-Yan processes at RHIC and GSI.