Color-Octet Contributions in the Associate J/psi+gamma Hadroproduction

TL;DR

This paper tests the color-octet mechanism within NRQCD for the associated production of J/psi and a photon in hadronic collisions. It computes both color-singlet and color-octet contributions, using NRQCD factorization and input color-octet matrix elements fitted from inclusive J/psi production data. The findings show color-octet channels are negligibly small relative to the color-singlet gluon-gluon fusion process across most kinematic regions, with only a high-p_T crossover where octet effects could appear but remain subdominant. The results reinforce the utility of J/psi+gamma production as a clean probe of the gluon distribution and heavy-quarkonium production mechanisms, suggesting kinematic cuts (e.g., p_T<6 GeV) to maintain this channel’s diagnostic power.

Abstract

Color-octet contributions to the associate J/psi+gamma hadroproduction are studied in detail, and found to be negligible, compared to the ordinary color-singlet contribution. Within the color-singlet model the J/psi+gamma production in the leading order is possible only through gluon-gluon fusion process. Therefore, the associate J/psi+gamma hadroproduction remains to be useful as a clean channel to probe the gluon distribution inside proton, to study heavy quarkonia production mechanism, and to find proton's spin structure.

Figures (8)

• Figure 1:
• Figure 2:
• Figure 3:
• Figure 4:
• Figure 5: