J/psi production via initial state radiation in e+ e- --> mu+ mu- gamma at an e+e- center-of-mass energy near 10.6 GeV

TL;DR

This study measures the production cross section and decay widths of J/psi via initial state radiation in e+e- collisions near 10.6 GeV, using BaBar data to improve understanding of J/psi properties.

Contribution

First measurement of J/psi production via initial state radiation at B-factory energies, providing precise decay widths and cross sections.

Findings

Measured Gamma(J/psi --> e+e-) as 5.61 keV

Derived total width of J/psi as 94.7 keV

Used 88.4 fb^-1 data from BaBar detector

Abstract

We have used a study of the process e+e- --> mu+ mu- gamma at a center-of-mass energy near the Y(4S) resonance for a mu+ mu- invariant mass range near the J/psi mass to extract the cross section sigma(e+e- --> J/psi gamma --> mu+ mu- gamma). The data set, corresponding to an integrated luminosity of 88.4 fb-1, was collected using the BaBar detector at the PEP-II collider. We measure the product Gamma(J/psi --> e+e-)B(J/psi --> mu+ mu-) to be 0.330 +/- 0.008(stat) +/- 0.007(syst) keV. Using the world averages for B(J/psi --> mu+ mu-) and B(J/psi --> e+e-), we derive the J/psi electronic and total widths: Gamma(J/psi --> e+e-)=5.61+/-0.20 keV and Gamma=94.7+/-4.4 keV.