Effective Sivers function
JINR, Bogoliubov Laboratory of Theoretical Physics, 141980 Dubna, Russia
Corresponding author: firstname.lastname@example.org
The effective (non-universal) nature of Sivers function reflects the process dependence of the imaginary phase required for T-odd Single Spin asymmetry. The explicit account for the phase allows to relate T-odd and T-even Spin asymmetries. The soft-gluon twist 3 contributions to single-spin asymmetries (SSA) in hard processes may be expressed in the form of effective T-odd Sivers distributions, whose signs and scales are modified by process-dependent colour factors. The Sivers mechanism is applied at large transverse momenta and the emission of balancing gluons provide the colour flow explaining this factor.
© EDP Sciences, Springer-Verlag, 2008