J/ψ polarization and pT distribution in cc¯ associated hadroproduction at O(αs5)

The quarkonium production in association with a heavy-quark pair of the same flavor was found to play an important role in various production schemes and provide a distinctive signature that could be studied in experiment. Within the nonrelativistic QCD framework, we perform the first complete calculation of the hadroproduction process gg→J/ψ+cc¯ at the next-to-leading order (NLO) in the expansion of strong coupling constant αs. The result tells us that the NLO corrections substantially enhance the color-singlet yield and alter the predicted polarization patterns and, hence, lead to a better agreement with experimental data across the pT spectrum. In contrast to charm-quark fragmentation, the fixed-order J/ψ and cc¯ associated production channel displays a markedly different kinematic behavior. While the inclusion of this process greatly reduces the discrepancy between color-singlet theoretical prediction and experimental measurement, a residual gap of approximately 1 order of magnitude still remains.