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.

Comments: 4 pages, 3 figures,