### Abstract

We calculate the contributions from QED processes involving two virtual photons to the cross sections for e ^{+}e ^{-} annihilation into two charmonium states with the same C parity. Genetically, the cross sections are three orders of magnitude smaller than those for charmonia with opposite C parity because they are suppressed by a factor of α ^{2}/ α _{s} ^{2}. However, if both charmonia have quantum numbers J ^{pc} = 1 ^{-}, then there is a contribution to the cross section that involves the fragmentation of each photon into a charmonium. The fragmentation contribution is enhanced by powers of E _{beam}/m _{c}, the ratio of the beam energy to the charm-quark mass, and this enhancement can compensate for the suppression factor that is associated with the coupling constants. In particular, the predicted cross section for J/ψ+J/ψ at the B factories is larger than that for J/ψ + η _{c}.

Original language | English |
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Article number | 054023 |

Journal | Physical Review D |

Volume | 67 |

Issue number | 5 |

DOIs | |

Publication status | Published - 2003 Dec 1 |

Externally published | Yes |

### ASJC Scopus subject areas

- Physics and Astronomy (miscellaneous)
- Physics and Astronomy(all)
- Nuclear and High Energy Physics
- Mathematical Physics

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## Cite this

^{+}e

^{-}annihilation into two virtual photons.

*Physical Review D*,

*67*(5), [054023]. https://doi.org/10.1103/PhysRevD.67.054023, https://doi.org/10.1103/PhysRevD.67.054023