Speaker
Description
In two π + W induced Drell-Yan experiments at CERN and Fermilab, angular distributions of the resultant dimuons showed a violation of the Lam-Tung relation, a perturbative QCD, “Callan-Gross-like” relationship between the polar and azimuthal angles made by the initial hadronic plane and final state dimuon plane in the Collins-Soper frame. At these energies, the violation manifests itself as a nonzero cos(2φ) modulation in dimuon azimuthal distributions, naively suggesting a double spin-flip in a single photon process or a contribution from the Boer-Mulders distribution, a transverse momentum dependent distribution function describing the correlation of motion of unpolarized nucleons with their constituent polarized partons. Fermilab Experiment 866/NuSea saw a Lam-Tung violation in p+d induced Drell-Yan characterized by a smaller cos(2φ) dimuon azimuthal modulation while p+p induced Drell-Yan saw results consistent with no violation of the relation. Fermilab Experiment 906/SeaQuest is currently investigating the possible violation of the Lam-Tung relation at a higher target x range than any previous Drell-Yan experiment. Studies of the angular distributions of p+p dimuons in SeaQuest will be presented.
