21 research outputs found
The cos 2 phi asymmetry of Drell-Yan and J/psi production in unpolarized ppbar scattering
We investigate the cos 2 phi azimuthal asymmetry in Drell--Yan and J/psi
production from unpolarized ppbar scattering at GSI-HESR energies. The
contribution to this asymmetry arising from the leading-twist Boer-Mulders
function h_1^perp(x, k_T^2), which describes a correlation between the
transverse momentum and the transverse spin of quarks in an unpolarized hadron,
is explicitly evaluated, and predictions for the GSI-HESR kinematic regime are
presented. We show that the cos 2 phi asymmetry is quite sizable both on the
J/psi peak and in the Drell-Yan continuum region. Therefore these processes may
offer an experimentally viable access to the Boer-Mulders function in the early
unpolarized stage of GSI experiments.Comment: 5 pages, 3 figures, to be published in Eur. Phys.