J/\psi Production Via Photon Fragmentation at Hadron Colliders

Abstract

The transverse momentum ($p_t$) distributions of production and polarization for $J/\psi$ 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 suggest a new mechanism for $J/\psi$ production at hadron collider, $pp(\bar p)\to \gamma^{\ast}(J/\psi)+X$ with $J/\psi$ from a virtual photon $\gamma^{\ast}$ fragmentation. Our calculations show it's $p_t$ distribution at NLO will be larger than that of the conventional $J/\psi$ production from the color-singlet mechanism at NLO when $p_{t}>26$ (35) GeV at the Tevatron (LHC) and reach about 6 (10) times of the conventional one when $p_t=50$ (100) GeV at the Tevatron (LHC), in spite of a suppression factor $(\alpha/\alpha_s)^2$ that is associated with the QED and QCD coupling constants. In addition, it also has large impact on the $p_{t}$ distribution of $J/\psi$ polarization in large $p_{t}$ region. Therefore, it is a important mechanism for $J/\psi$ production at large $p_t$ region especially for the LHC.