Measurement of the ratio of the leptonic widths $\hat{I}{“}_{ee}/\hat{I}{“}_{\hat{I}¼\hat{I}¼}$ for the $J/\ddot{I}ˆ$ meson

Abstract

The ratio of the electron and muon widths of the $J/\ddot{I}ˆ$ meson has been measured using direct $J/\ddot{I}ˆ$ decays in the KEDR experiment at the VEPP-4M electron-positron collider. The result $\hat{I}{“}_{ee}(J/\ddot{I}ˆ)/\hat{I}{“}_{\hat{I}¼\hat{I}¼}(J/\ddot{I}ˆ)=1.0022\pm 0.0044\pm 0.0048(0.65\%)$ is in good agreement with the lepton universality. The experience collected during this analysis will be used for a $J/\ddot{I}ˆ$ lepton width determination with up to 1% accuracy.

5 pages, 6 figures, 2 tables