Azimuthal dependence in unpolarized proton-induced Drell-Yan process

For unpolarized Drell-Yan process, a $\cos(2\phi)$ azimuthal distribution could arise from the presence of a chiral-odd, transverse-momentum dependent quark distribution function, $h_1^{\perp}$. In quark-diquark model, $h_1^{\perp}$ is equal to the Sivers function. Both the Sivers function and the $h_1^{\perp}$ are predicted to undergo a sign-change in the Drell-Yan process as compared to the Semi-Inclusive Deep-Inelastic scattering. A significant $\cos(2\phi)$ distribution has been observed in pion-induced Drell-Yan process and has been interpreted in terms of the $h_1^{\perp}$ distribution function. Additional information on the origin of the $cos(2\phi)$ dependence could be obtained from an analysis of the unpolarized proton-induced Drell-Yan data. Preliminary results from an analysis of the Fermilab E866 800 GeV p+p and p+d Drell-Yan data for the $\cos(2\phi)$ azimuthal distribution will be presented.