https://doi.org/10.1140/epjc/s2005-02136-x
theoretical physics
Collins effect in single spin asymmetries of the 
process
1
Department of Physics, Peking University, 100871, Beijing, P.R. China
2
Di.S.T.A., Universitá del Piemonte Orientale “A. Avogadro” and INFN, Gruppo Collegato di Alessandria, 15100, Alessandria, Italy
3
Departamento de Física, Universidad Técnica Federico Santa María, Casilla 110-V, Valparaíso, Chile
4
Department of Physics, Nanjing Normal University, 210097, Nanjing, P.R. China
5
Institut für Theoretische Physik, Universität Regensburg, 93040, Regensburg, Germany
* e-mail: mabq@phy.pku.edu.cn
We investigate the Collins effect in single spin asymmetries (SSAs) of the process by taking into account the transverse momentum dependence of the microscopic sub-process cross sections, with the transverse momentum in the Collins function integrated over. We find that the asymmetries due to the Collins effect can only explain the available data at best qualitatively, by using our choices of quark distributions in the quark-diquark model and a pQCD-based analysis, together with several options of the Collins function. Our results indicate the necessity to take into account contributions from other effects such as the Sivers effect or twist-3 contributions.
© Springer-Verlag, 2005
