Measurement of Double Charmonium Production in $e^+e^-$ Annihilations at $\sqrt{s}=10.6$ GeV

Abstract

We study $e^+e^-\to J/ψc\bar{c}$ by measuring the invariant mass distribution recoiling against fully reconstructed $J/ψ$ decays, using 124 fb$^{-1}$ of data collected with a center-of-mass energy of 10.6 GeV with the $BaBar$ detector. We observe signals for $η_c(1S)$, $χ_{c0}$, and $η_c(2S)$ in the recoil mass distribution, thus confirming previous measurements. We measure $σ(e^+e^-\to J/ψ+c\bar{c}) {\cal B} (c\bar{c} \to >2 \mathrm{charged})$ to be $17.6\pm2.8\textrm{(stat)}^{+1.5}_{-2.1}\textrm{(syst)}$ fb, $10.3\pm2.5\textrm{(stat)}^{+1.4}_{-1.8}\textrm{(syst)}$ fb, and $16.4\pm3.7\textrm{(stat)}^{+2.4}_{-3.0}\textrm{(syst)}$ fb with $c\bar{c}=η_c(1S)$, $χ_{c0}$, and $η_c(2S)$, respectively.

Figures (2)

• Figure 1: Distributions of (a) $\cos\theta_l$ and (b) $E_\textrm{QED}-E_\textrm{beams}$ in the data, (c) $\cos\theta_l$ and (d) $E_\textrm{QED}-E_\textrm{beams}$ in the signal Monte Carlo. The arrows point to where the selection criteria are applied.
• Figure 2: The fit to the recoil mass distribution is represented by the solid curve. The dashed curve is a second-order polynomial representing the background. The points with error bars refer to the events in the ${J / \psi }\xspace$ mass window. The histograms represent different sources of backgrounds.