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Measurement of $J/ψ$ production in continuum $e^+e^-$ annihilations near $\sqrt s = 10.6$ GeV

The BABAR Collaboration, B. Aubert

Abstract

The production of $J/ψ$ mesons in continuum $e^+e^-$ annihilations has been studied with the BABAR detector at energies near the $Υ(4S)$ resonance, approximately 10.6 GeV. The mesons are distinguished from $J/ψ$ production in B decays through their center-of-mass momentum and energy. We measure the cross section $e^+e^-\to J/ψX$ to be $2.52\pm 0.21\pm 0.21$ pb; for momentum above 2 GeV/c, it is $1.87\pm 0.10\pm 0.15$ pb. We set a 90% confidence level upper limit on the branching fraction for direct $Υ(4S)$\to J/ψX$ decays at $4.7\times 10^{-4}$.

Measurement of $J/ψ$ production in continuum $e^+e^-$ annihilations near $\sqrt s = 10.6$ GeV

Abstract

The production of mesons in continuum annihilations has been studied with the BABAR detector at energies near the resonance, approximately 10.6 GeV. The mesons are distinguished from production in B decays through their center-of-mass momentum and energy. We measure the cross section to be pb; for momentum above 2 GeV/c, it is pb. We set a 90% confidence level upper limit on the branching fraction for direct \to J/ψX4.7\times 10^{-4}$.

Paper Structure

This paper contains 3 equations, 4 figures.

Figures (4)

  • Figure 1: ${J / \psi }$ signal events observed as a function of visible energy $E$ in the (a) $e^+e^-$ and (b) $\mu^+\mu^-$ final states; $R_2$ distribution for (c) $e^+e^-$ and (d) $\mu^+\mu^-$. The histogram is the predicted ISR background that has been subtracted from data; the filled histogram is the ISR ${\psi(2S)}$ component only. A requirement of $\ge 5$ tracks is applied to the $e^+e^-$ sample; applying it to the $\mu^+\mu^-$ sample produces the dashed histogram. Event preselection requires $E>4$$\mathrm{\,Ge V}$ and $R_2<0.95$.
  • Figure 2: Mass distribution of ${J / \psi }$ candidates reconstructed in data recorded below the $焇{(4S)}$ resonance in the (a) $e^+e^-$ and (b) $\mu^+\mu^-$ final states. Mass distributions for ${p^*} > 2$${\mathrm{\,Ge V\!/}c}$ in data at the $焇{(4S)}$ resonance in (c) $e^+e^-$ and (d) $\mu^+\mu^-$ final states. The number of ${J / \psi }$ mesons extracted by a fit to the distribution is shown on each graph.
  • Figure 3: Center of mass momentum distribution of ${J / \psi }$ mesons produced in continuum $e^+e^-$ annihilation.
  • Figure 4: (a) Production angle (${\cos\theta^*}$) distribution for ${J / \psi }$ mesons produced in continuum $e^+e^-$ annihilation; (b) helicity (${\cos\theta_H}$) distribution. Solid curve is the fit to ${p^*} < 3.5$${\mathrm{\,Ge V\!/}c}$; dashed curve is for ${p^*} > 3.5$${\mathrm{\,Ge V\!/}c}$.