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

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.

Comments: 5 pages, 2 figures, 1 table, revised to correct errors in original version, Erratum to Phys. Rev. Lett. article included as a separate file