Azimuthal angle dependence of di-jet production in unpolarized hadron scattering

We study the azimuthal asymmetry of back-to-back di-jet production in unpolarized hadron scattering, arising from the product of two Boer-Mulders functions, which describe the transverse spin distribution of quarks inside an unpolarized hadron. We find that there is a cos δφ angular dependence of the di-jet, with δφ the difference of the azimuthal angle of tow jets respectively. In the case of Jq+Jq production, we find that there is a color factor enhancement in the gluonic cross-section due to the multiple initial-/final-state interactions, compared with the result from the standard generalized parton model. We estimate the cos δφ asymmetry of the total di-jet production at RHIC, showing that the color factor enhancement in the azimuthal asymmetric cross section of Jq+Jq production will reverse the sign of the asymmetry.