Observation of Double cc bar Production in e+ e- Annihilation at sqrt{s} ~ 10.6 GeV

TL;DR

This paper reports the first observation of double ccbar production in e+e- annihilation at around 10.6 GeV, measuring cross-sections and demonstrating the process's significance in charmonium production studies.

Contribution

It provides the first experimental evidence of double ccbar production in e+e- collisions at this energy, with detailed cross-section measurements and analysis methods.

Findings

Observation of prompt J/psi via double ccbar production.

Measured cross-sections for J/psi eta_c and J/psi D*+ production.

The ratio of double ccbar to total J/psi production is approximately 0.59.

Abstract

We report the observation of prompt J/psi via double ccbar production from the e+e- continuum. In this process one ccbar pair fragments into a J/psi meson while the remaining pair either produces a bound charmonium state or fragments into open charm. Both cases have been observed: the first by studying the mass spectrum of the system recoiling against the J/psi, and the second by reconstructing the J/psi together with a charmed meson. We find cross-sections of \sigma(e+ e- -> J/psi eta_c (gamma)) * BR (eta_c -> >=4 charged) = 0.033 (+0.007 -0.006)(stat) \pm 0.009(syst)pb and \sigma(e+ e- -> J/psi D*+ X) = 0.53 (+0.19 -0.15)(stat) \pm 0.14(syst) pb, and infer \sigma(e+ e- -> J/psi c cbar) / \sigma(e+ e- -> J/psi X) = 0.59 (+0.15 -0.13)(stat) \pm 0.12(syst). These results are obtained from a 46.2/fb data sample collected near the Upsilon(4S) resonance, with the Belle detector at the KEKB asymmetric energy e+ e- collider.