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

• Published in: Physics letters. B Vol. 772; no. C; pp. 283 - 289
• Main Authors: Efremov, A.V., Ivanov, N.Ya, Teryaev, O.V.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 10-09-2017; Elsevier
• Subjects: Azimuthal asymmetry; Charm leptoproduction; COMPASS; QCD; COMPASS; QCD; Azimuthal asymmetry; Charm leptoproduction
• ISSN: 0370-2693; 1873-2445
• DOI: 10.1016/j.physletb.2017.06.057

We present the QCD predictions for the azimuthal cos⁡2φ 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⁡2φ 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⁡2φ 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⁡2φ asymmetry as a probe of the gluonic analogue of the Boer–Mulders function, h1⊥g, describing the linear polarization of gluons inside unpolarized proton.