e^+ e^- Annihilation into J/psi + J/psi

TL;DR

It is suggested that a significant part of the discrepancy can be explained by the process e(+)e(-)-->J/psi+J/PSi, which can proceed through fragmentation of two virtual photons into two cc pairs and its cross section may be larger than that for J/pso+eta(c) by about a factor of 3.7.

Abstract

Recent measurements by the Belle Collaboration of the exclusive production of two charmonia in e^+ e^- annihilation differ substantially from theoretical predictions. We suggest that a significant part of the discrepancy can be explained by the process e^+ e^- -> J/psi + J/psi. Because the J/psi + J/psi production process can proceed through fragmentation of two virtual photons into two cc-bar pairs, its cross section may be larger than that for J/psi +eta_c by about a factor 1.8, in spite of a suppression factor alpha^2/alpha_s^2 that is associated with the QED and QCD coupling constants.

Figures (2)

• Figure 1: QED diagrams for $e^+ e^- \to \gamma^* \gamma^* \to c \bar{c} + c \bar{c}$. The upper and lower $c\bar{c}$ pairs evolve into $H_1$ and $H_2$, respectively.
• Figure 2: Differential cross sections $d\sigma/d|x|$ for $e^+ e^-$ annihilation into $J/\psi+J/\psi$ and $J/\psi+\eta_c$ at $E_{\rm beam} = 5.3$ GeV. The areas under the curves are the integrated cross sections 6.65 fb and 3.78 fb. There are large errors associated with QCD and relativistic corrections, as described in the text.