Measurement of J/Ψ and Ψ' 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/Ψ and Ψ' 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/Ψ and Ψ' 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/Ψ and Ψ' ratios to be consistent with unity. The absolute cross sections for J/Ψ and Ψ' production have also been extracted and compared with theoretical calculations.