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

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 $4.7\times 10^{-4}$.