The $\cos2\phi$ azimuthal asymmetry of unpolarized $p\bar{p}$ collisions   at Tevatron
  We calculate the $\cos2\phi$ azimuthal asymmetry of the unpolarized $p\bar{p}$ Drell-Yan dilepton production process in the $Z$-resonance region at the Tevatron kinematic domain. Such an azimuthal asymmetry can provide additional information about a spin-related new parton distribution function, i.e., the Boer-Mulders function of the proton, compared to the $pp$ process. Therefore the available data of unpolarized proton-antiproton collision at Tevatron can contribute to our study on the spin structure of the nucleon. 
Tianbo Liu, Bo-Qiang Ma
hep-ph