Observation ofϒ,ϒ′, andϒ′′at the Cornell Electron Storage Ring

Abstract

The $\Upsilon$, ${\Upsilon }^{\prime }$, and ${\Upsilon }^{\prime \prime }$ states have been observed at the Cornell Electron Storage Ring as narrow peaks in $\sigma (e^{+}{e}^{-}\to \mathrm{hadrons})$ versus beam energy. Data were collected during a run with integrated luminosity of 1000 ${\mathrm{nb}}^{-1\mathrm{}}$, using the Columbia University-Stony Brook segmented NaI detector. The measured mass differences are $M\left({\Upsilon }^{\prime }\right)-M\left(\Upsilon \right)=559\mathrm{}\pm 1(\pm 3)$ MeV and $M\left({\Upsilon }^{\prime \prime }\right)-M\left(\Upsilon \right)=889\mathrm{}\pm 1(\pm 5)$ MeV, where the errors in parentheses represent systematic uncertainties. Preliminary values for the leptonic width ratios were also obtained.