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On the cos 2 phi asymmetry in unpolarized leptoproduction

Vincenzo Barone, Zhun Lu, Bo-Qiang Ma

hep-pharXiv:hep-ph/0512145

Abstract

We investigate the origin of the cos 2 phi azimuthal asymmetry in unpolarized semiinclusive DIS. The contributions to this asymmetry arising from the intrinsic transverse motion of quarks are explicitly evaluated, and predictions for the HERMES and COMPASS kinematic regimes are presented. We show that the effect of the leading-twist Boer-Mulders function h1perp(x, kT2), which describes a correlation between the transverse momentum and the transverse spin of quarks, is quite significant and may also account for a part of the cos 2 phi asymmetry measured by ZEUS in the perturbative domain.

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