Measurement of the e+e- -> J/psi ccbar cross section at \sqrt{s} ~10.6 GeV

TL;DR

This paper reports a precise measurement of the cross section for e+e- annihilation into J/psi and ccbar pairs at around 10.6 GeV, using innovative techniques to identify two-body final states without full reconstruction.

Contribution

It introduces a recoil mass technique to measure the e+e- -> J/psi ccbar cross section, providing new experimental data at B-factory energies.

Findings

Measured cross section for e+e- -> J/psi ccbar: 0.74 pb

Measured non-ccbar J/psi cross section: 0.43 pb

Analysis based on 673/fb data sample near Upsilon(4S)

Abstract

We present a new measurement of the e+e- -> J/psi ccbar cross section where the ccbar pair can fragment either into charmed hadrons or a charmonium state. In the former case the J/psi and a charmed hadron are reconstructed, while the latter process is measured using the recoil mass technique, which allows the identification of two-body final states without reconstruction of one of the charmonia. The measured e+e- -> J/psi ccbar cross section is (0.74 +- 0.08 + 0.09 - 0.08) pb, and the e+e- -> J/psi non-ccbar cross section is (0.43 +- 0.09 +-0.09) pb. We note that the measured cross sections are obtained from a data sample with the multiplicity of charged tracks in the event larger than four; corrections for the effect of this requirement are not performed as this cannot be done in a model-independent way. The analysis is based on a data sample with an integrated luminosity of 673/fb recorded near the Upsilon(4S) resonance with the Belle detector at the KEKB e+e- asymmetric-energy collider.