$J/\psi$ Pair Hadroproduction at Next-to-Leading Order in Nonrelativistic-QCD at CMS

We perform a complete study on the $J/\psi$ pair hadroproduction at next-to-leading order (NLO) in the nonrelativstic-QCD (NRQCD) framework with the pair of $c\bar{c}$ either in ${}^{3}S_1^{[1]}$ or ${}^{1}S_0^{[8]}$ fock state. It is found that the ${}^{1}S_0^{[8]}$ channel contribution at NLO is essential. Our results indicate that for the CMS, the NRQCD predictions can not describe the experimental data at all, and the total cross section predicted by NRQCD is smaller than the experimental data by an order of magnitude. So new mechanisms are needed to understand the CMS data for $J/\psi$ pair production.