Instanton contribution to the Sivers function
arXiv:hep-ph/0606238 · doi:10.1016/j.physletb.2006.09.019
Abstract
We study the Sivers function for valence u and d quarks in the proton within the instanton model for QCD vacuum, adopting the MIT bag model wave functions for quarks. Within approaches based on perturbative one-gluon final state interactions a non-zero value of the Sivers function is related to the presence of both S and P wave components in quark wave functions. We show that the instanton-induced chromomagnetic, nonperturbative interaction leads to very specific spin-spin correlations between the struck and spectator quarks, resulting in a non-trivial flavour dependence of the Sivers function. Comparison of the obtained Sivers functions with phenomenological parameterizations is discussed.
1+12 pages, 4 ps figures; v2: few references and one sentence added in the introduction; final version published in Phys. Lett. B
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