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

Abstract

In this work, we calculate the next-to-leading-order (NLO) QCD corrections to the process $p+p \to J/ψ+ γ$ via the color-singlet mechanism at the LHC. The results show that the partial cross section ($p_t^{J/ψ}>$3GeV and $|y^{J/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.

Figures (6)

• Figure 1: Transverse momentum distribution of $J/\psi$ production with $\mu_r=\mu_f=\sqrt{(2m_c)^2+p_t^2}$ at the LHC.
• Figure 2: Transverse momentum distribution of $\Upsilon$ production with $\mu_r=\mu_f=\sqrt{(2m_b)^2+p_t^2}$ at the LHC.
• Figure 3: Transverse momentum dependence of $J/\psi$ polarization with $\mu_r=\mu_f=\sqrt{(2m_c)^2+p_t^2}$ at the LHC.
• Figure 4: Transverse momentum dependence of $\Upsilon$ polarization with $\mu_r=\mu_f=\sqrt{(2m_b)^2+p_t^2}$ at the LHC.
• Figure 5: The $\mu$ dependence of the partial cross section ($p_t^{J/\psi(\Upsilon)}>$3GeV) with $\mu_0=\sqrt{(M_{J/\psi(\Upsilon)})^2+p_t^2}$.