Next-to-Leading-Order QCD corrections to J/ψ(Υ)+γproduction at the LHC

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In this work, we calculate the next-to-leading-order (NLO) QCD corrections to the process p+p → J/ψ+ γ via the color-singlet mechanism at the LHC. The results show that the partial cross section (pₜʲ/ψ>3GeV and |yʲ/ψ,γ|<3) is enhanced by a factor of about 2.0, and the differential cross section can be enhanced by two orders of magnitude in the large transverse momentum region of J/ψ. Furthermore, the polarization of J/ψ changes from transverse polarization at leading-order to longitudinal polarization at NLO. For the inclusive J/ψ hadroproduction, it is known that the color-octet contributions are one order of magnitude larger than the color-singlet contribution, and the polarization distribution is dominated by the color-octet behavior at NLO. In contrast, for J/ψ+γ production the color-singlet contribution is of the same order as the color-octet contribution, and the polarization distribution arises from both the color-singlet and color-octet. Therefore, measurements of J/ψ production associated with a direct photon at the hadron collider could be an important supplement to testify the theoretical framework treating with the heavy quarkonium. In addition, an NLO QCD correction to Υ+γ production at the LHC is also presented in this paper.