Inclusive J/𝜓 production in forward proton-proton and proton-lead collisions at high energy

We calculate the cross section for forward J/𝜓 production in proton-proton and minimum bias proton-lead collisions using the color glass condensate (CGC) and nonrelativistic QCD (NRQCD) formalism consistently with deep inelastic scattering data. The cross section for color singlet states is sensitive to a four-point correlator of Wilson lines for which we describe in the Gaussian approximation in the large-𝑁𝑐 limit. Furthermore, we quantify the importance of finite-𝑁c corrections to have a small ∼12% effect. In contrast with the generic NRQCD expectation, we show that the color singlet contribution is only 15% to the total cross section. We also compare our predictions for J/𝜓 production as well as for the nuclear modification ratio 𝑅𝑝⁢𝑃⁢𝑏 to LHCb and ALICE data. We find a good agreement at forward rapidities, except at low transverse momenta where the cross sections are overestimated.