Polarization asymmetry in dilepton production in perturbative quantum chromodynamics

Abstract

Quantum-chromodynamics (QCD) evolution equations together with angular momentum sum rules are used to examine the polarization structures of the quark sea and gluons in hadrons. It is shown that it is possible to sustain large polarizations of the flavor-singlet components and they would in turn imply large asymmetries in the dilepton production by polarized beam on polarized target, which can be calculated in perturbative QCD. At high q_T for the μ⁺μ^- pair, the main contributing diagram is quark-gluon Compton scattering, and the extent of gluon polarization is expected to be revealed in this kinematic region. At lower q_T the quark-antiquark annihilation diagram becomes increasingly important and correspondingly polarized-sea-quark-induced asymmetries are to be found in this region. Further, since the polarization depends on the number of flavors excited, as the available energy in the hadron collision changes, the magnitude of asymmetries should show dramatic variations.