Study of double charmonium production in e^+ e^- annihilation at \sqrt{s} ~ 10.6 GeV

Abstract

We present a new analysis of double charmonium production in e^+ e^- annihilation. The observation of the processes e^+ e^- -> J/psi eta_c, J/psi chi_c0, and J/psi eta_c(2S) is confirmed using a dataset more than three times larger than that of Belle's previous report, and no evidence for the process e^+ e^- -> J/psi J/psi is found. We perform an angular analysis for J/psi eta_c production and set an upper limit on the production of J/psi J/psi. Processes of the type e^+ e^- -> psi(2S) (cc)_res have been observed for the first time; their rates are found to be comparable to those of e^+ e^- -> J/psi (cc)_res processes.

Figures (4)

• Figure 1: The mass of the system recoiling against the reconstructed $J/\psi$ in inclusive $e^+e^- \to J/\psi\,X$ events. The curves are described in the text.
• Figure 2: The square of the mass of the system recoiling against the reconstructed $\psi(2S)\to J/\psi\, \pi^+ \pi^-$, in events with charged multiplicity equal to 4. Points with error bars show the data, the solid line shows the result of the fit described in the text. The hatched histogram (scarcely visible) shows the spectrum in the scaled $\psi(2S)$ sidebands.
• Figure 3: Distributions of cosines of the production (left) and $J/\psi$ helicity angles (right) for $e^+ e^- \to J/\psi\,\eta_c$ (top row), $e^+ e^- \to J/\psi\,\chi_{c0}$ (middle row) $e^+ e^- \to J/\psi\,\eta(2S)$ (bottom row). The solid lines are results of the individual fits; the dotted lines are the simultaneous fit results.
• Figure 4: The mass of the system recoiling against the reconstructed $\psi(2S)$ in inclusive $e^+e^- \to \psi(2S) X$ events. The curves are described in the text.