Azimuthal dependence of the heavy quark initiated contributions to DIS

Abstract

We analyze the azimuthal dependence of the heavy-quark-initiated contributions to the lepton-nucleon deep inelastic scattering (DIS). First we derive the relations between the parton-level semi-inclusive structure functions and the helicity {gamma}*Q cross sections in the case of arbitrary values of the heavy quark mass. Then the azimuth-dependent O({alpha}{sub s}) lepton-quark DIS is calculated in the helicity basis. Finally, we investigate numerically the properties of the cos{phi} and cos2{phi} distributions caused by the photon-quark scattering (QS) contribution. It turns out that, contrary to the basic photon-gluon fusion (GF) component, the QS mechanism is practically cos2{phi}-independent. This fact implies that measurements of the azimuthal distributions in charm leptoproduction could directly probe the charm density in the proton.