Cos2phi Asymmetry in Proton-induced Drell-Yan

Lingyan Zhu
University of Illinois at Urbana-Champaign

Large cos2phi azimuthal asymmetry was observed in upolarized pion-induced
Drell-yan. There are a few theoretical attempts to explain it. The most
popular one connects the cos2phi asymmetry to the Boer-Mulders
functions, a time-odd transverse-momentum-dependent parton
distribution similar to Siver function. New data will help to justify
different theoretical models. I will review the current status and present
the recent results from Fermilab E866 collaboration on the cos2phi
asymmetry in unpolarized proton-induced Drell-Yan.