Measurement of $J/\psi$ and $\psi^\prime$ production in p + p and p + d interaction with 120 GeV proton beam in the Fermilab SeaQuest experiment

High-mass dimuon production in $p + p$ and $p + d$ interaction has been measured in the SeaQuest experiment with 120 GeV proton beam at Fermilab. The dimuon events measured in SeaQuest contain both the Drell-Yan and the $J/\psi$ and $\psi^\prime$ production. Unlike the Drell-Yan process which probes the antiquark distributions in the nucleons, the charmonium production is sensitive to both quark and gluon distributions. We report the measurement of the $(p + d) / 2 (p + p)$ cross section ratios for $J/\psi$ and $\psi^\prime$ over the kinematic region of $0.4 < x_F< 0.9$ and compare these ratios with that of the Drell-Yan events. Unlike the Drell-Yan, we find the $J/\psi$ and $\psi^\prime$ ratios to be consistent with unity. The absolute cross sections for $J/\psi$ and $\psi^\prime$ production have also been extracted and compared with theoretical calculations.