Leptonic Decays of Vector Mesons: the Branching Ratio of the Electron-Positron Decay Mode of the Phi Meson

Abstract

An experiment designed to measure the branching ratio of the phi meson to ${e}^{+}{e}^{\ensuremath{-}}$ was performed at DESY by measuring phi production and phi decay to ${e}^{+}{e}^{\ensuremath{-}}$ with the same apparatus. The results of this experiment, based on ${10}^{4}$ $\ensuremath{\phi}\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}$ events and 41 $\ensuremath{\phi}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}$ events on carbon, yield a branching ratio of (2.9\ifmmode\pm\else\textpm\fi{}0.8)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$. This result is compared with various theoretical predictions.