J/ψProduction Via Photon Fragmentation at Hadron Colliders

Abstract

The transverse momentum ($p_t$) 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 suggest a new mechanism for $J/ψ$ production at hadron collider, $pp(\bar p)\to γ^{\ast}(J/ψ)+X$ with $J/ψ$ from a virtual photon $γ^{\ast}$ fragmentation. Our calculations show it's $p_t$ distribution at NLO will be larger than that of the conventional $J/ψ$ 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 $(α/α_s)^2$ that is associated with the QED and QCD coupling constants. In addition, it also has large impact on the $p_{t}$ distribution of $J/ψ$ polarization in large $p_{t}$ region. Therefore, it is a important mechanism for $J/ψ$ production at large $p_t$ region especially for the LHC.

Figures (3)

• Figure 1: Typical Feynman Diagrams for $J/\psi$ production through photon fragmentation at LO(B1, B2), virtual corrections(V1,V2) and real corrections(R1--R5).
• Figure 2: (a) The $\mu$ dependence of the cross section for the photon fragmentation $J/\psi$ production at the Tevatron(lower) and LHC(upper) at LO(dashed) and NLO(solid) with $\mu_{r}=\mu_{f}=\mu$. The $p_{t}$ distribution for $J/\psi$ production at the Tevatron(b) and LHC(c). "QED" refers to the photon fragmentation production, "QCD" refers to the conventional production from the CSM, and "total" refers to the QED+QCD. The center-of-mass energies are 1.98 TeV at Tevatron and 14 TeV at LHC.
• Figure 3: The $p_{t}$ dependence of the polarization parameter $\alpha$ for $J/\psi$ production at Tevatron(left) and LHC (right).