Li, R (reprint author), Chinese Acad Sci, Inst High Energy Phys, POB 918 4, Beijing 100049, Peoples R China.
In this work, we calculate the next-to-leading-order (NLO) QCD corrections to the process p + p -> J/psi + gamma via the color-singlet mechanism at the LHC. The results show that the partial cross section (p(t)(J/psi) > 3 GeV and \y(J/psi.gamma)\ < 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/psi. Furthermore, the polarization of J/psi changes front transverse polarization at leading-order to longitudinal polarization at NLO. For the inclusive J/psi hadroproduction, it is known that the coloroctet 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/psi + gamma 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/psi 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 Gamma + gamma production at the LHC is also presented in this Letter. (C) 2009 Elsevier B.V. All rights reserved.