Complete Study of Hadroproduction of a $\Upsilon$ Meson Associated with   a Prompt $J/\psi$
  We present the first complete study of $\Upsilon$ and prompt $J/\psi$ production from single-parton scattering, including the complete $\mathcal{O}(\alpha_S^6)$ color-singlet contribution, the $\mathcal{O}(\alpha_S^2\alpha^2)$ electroweak contribution, the complete nonrelativistic S-wave and P-wave color-octet contribution as well as the feeddown contribution. Our study was motivated by the recent evidence reported by D0 Collaboration of prompt $J/\psi$ and $\Upsilon$ simultaneous production at the Tevatron. With our complete evaluation, we are able to refine the determination of the double parton scattering contribution made by D0 Collaboration. We find that the effective cross section characterizing the importance of double-parton scatterings is $\sigma_{\rm eff}\le 8.2$ mb at $68\%$ confidence level from the D0 measurement. 
Hua-Sheng Shao, Yu-Jie Zhang
hep-ph hep-ex nucl-ex nucl-th