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arXiv · 1706.03125

QCD predictions for the azimuthal asymmetry in charm leptoproduction for the COMPASS kinematics

A. V. Efremov·N. Ya. Ivanov·O. V. Teryaev
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Abstract

We present the QCD predictions for the azimuthal $\cos 2\varphi$ asymmetry in charm leptoproduction for the kinematics of the COMPASS experiment at CERN. The asymmetry is predicted to be large, about 15%. The radiative corrections to the QCD predictions for the $\cos 2\varphi$ distribution are estimated to be small, less than 10%. Our calculations show that the azimuthal asymmetry in charm production is well defined in pQCD: it is stable both perturbatively and parametrically, and practically insensitive to theoretical uncertainties in the input parameters. We analyze the nonperturbative contributions to the $\cos 2\varphi$ distribution due to the gluon transverse motion in the target and the $c$-quark fragmentation. Because of the $c$-quark low mass, the nonperturbative contributions are expected to be sizable, about (30--40)%. We conclude that extraction of the azimuthal asymmetries from available COMPASS data will provide valuable information about the transverse momentum dependent distribution of the gluon in the proton and the $c$-quark hadronization mechanism. Finally, we discuss the $\cos 2\varphi$ asymmetry as a probe of the gluonic analogue of the Boer-Mulders function, $h_{1}^{\perp g}$, describing the linear polarization of gluons inside unpolarized proton.

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A. V. Efremov, N. Ya. Ivanov, O. V. Teryaev. 2017-06-09. QCD predictions for the azimuthal asymmetry in charm leptoproduction for the COMPASS kinematics. https://doi.org/10.1016/j.physletb.2017.06.057

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