J/ψ production via photon fragmentation at hadron colliders

The transverse momentum (pt) distributions of production and polarization for J/ψ measured by CDF Collaboration are still challenging our understanding of the heavy quarkonium production mechanism even with recent significant theoretical progresses on the next-to-leading-order (NLO) QCD calculation. We investigate an interesting mechanism for J/ψ production at hadron collider, pp(p¯)→γ⁎(J/ψ)+X with J/ψ from a virtual photon γ⁎ fragmentation. Our calculations show that the J/ψpt distribution in the photon fragmentation process up to NLO in αs will be larger than that of the conventional J/ψ production from the color-singlet mechanism at NLO when pt>26 (35) GeV at the Tevatron (LHC) and reach about 6 (10) times of the conventional one when pt=50 (100) GeV at the Tevatron (LHC), in spite of a suppression factor (α/αs)2 that is associated with the QED and QCD coupling constants. In addition, it also has large impact on the pt distribution of J/ψ polarization in large pt region. Therefore, it is an important mechanism for J/ψ production at large pt region especially for the LHC.