Effective role of unpolarized nonvalence partons in Drell-Yan single spin asymmetries

Abstract

We perform numerical simulations of the Sivers effect from single spin asymmetries in Drell-Yan processes on transversely polarized protons. We consider colliding antiprotons and pions at different kinematic conditions of interest for the future planned experiments. We conventionally name "framework I" the results obtained when properly accounting for the various flavor dependent polarized valence contributions in the numerator of the asymmetry, and for the unpolarized nonvalence contribution in its denominator. We name "framework II" the results obtained when taking a suitable flavor average of the valence contributions and neglecting the nonvalence ones. We compare the two methods, also with respect to the input parametrization of the Sivers function which is extracted from data with approximations sometimes intermediate between frameworks I and II. Deviations between the two approaches are found to be small except for dilepton masses below 3 GeV. The Sivers effect is used as a test case; the arguments can be generalized to other interesting azimuthal asymmetries in Drell-Yan processes, such as the Boer-Mulders effect.

arXiv comment13 pages, 9 figures in eps format

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Cited by in corpus (4)

• A scheme for fast exploratory simulation of azimuthal asymmetries in Drell-Yan experiments at intermediate energies. The DY_AB Monte Carlo event generator
• Effects of azimuth-symmetric acceptance cutoffs on the measured asymmetry in unpolarized Drell-Yan fixed target experiments
• Extraction of finite-energy contributions to the Sivers asymmetry from the analysis of exclusive proton-proton scattering
• At the borderline between exclusive and inclusive physics: Study of Drell-Yan fragments in the PANDA experiment (A preliminary simulation)