Inclusive double-quarkonium production at the Large Hadron Collider

Based on the nonrelativistic QCD (NRQCD) factorization formalism, we investigate inclusive productions of two spin-triplet S-wave quarkonia pp → 2J/ψ + X, 2γ + X, and J/ψ + γ + X at the CERN Large Hadron Collider. The total production rates integrated over the rapidity (y) and transverse-momentum (p_T) ranges |y| < 2.4 and pt < 50 GeV are predicted to be σ[pp → 2J/ψ + X] =22 (35) nb, σ[pp → 2γ + X] = 24 (49) pb, and σ[pp → J/ψ + γ + X] =7 (13) pb at the center-of-momentum energy √s = 7 (14) TeV. In order to provide predictions that can be useful in both small-and large-pT regions, we do not employ the fragmentation approximation and we include the spin-triplet S-wave color-singlet and color-octet channels for each quarkonium final state at leading order in the strong coupling. The pT distributions of pp → 2 J/ψ + X and 2γ + X in the low-p_t region are dominated by the color-singlet contributions. At leading order in the strong coupling, the color-singlet channel is absent for pp → J/ψ + γ + X. Therefore, the process pp → J/ψ + γ + X may provide a useful probe to the color-octet mechanism of NRQCD.