Further experimental studies of two-body radiative<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>Υ</mml:mi></mml:math>decays

Abstract

Continuing our studies of radiative $\ensuremath{\Upsilon}$ decays, we report on a search for $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\Upsilon}}\ensuremath{\gamma}\ensuremath{\eta}$ and $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\Upsilon}}\ensuremath{\gamma}{f}_{J}(2220)$ in $61.3$ ${\mathrm{pb}}^{\ensuremath{-}1}$ of ${e}^{+}{e}^{\ensuremath{-}}$ data taken with the CLEO II detector at the Cornell Electron Storage Ring. For the $\ensuremath{\gamma}\ensuremath{\eta}$ search the three decays of the $\ensuremath{\eta}$ meson to ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0},$ ${\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}$, and $\ensuremath{\gamma}\ensuremath{\gamma}$ were investigated. We found no candidate events in the $(3\ensuremath{\pi}{)}^{0}$ modes and no significant excess over expected backgrounds in the $\ensuremath{\gamma}\ensuremath{\gamma}$ mode to set a limit on the branching fraction of $\mathcal{B}(\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\Upsilon}}\ensuremath{\gamma}\ensuremath{\eta})&lt;2.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ at $90%$ C.L. The three charged two-body final states $h\overline{h}(h={\ensuremath{\pi}}^{+}{,K}^{+},p)$ were investigated for ${f}_{J}(2220)$ production, with one, one, and two events found, respectively. Limits at $90%$ C.L. of $\mathcal{B}(\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\Upsilon}}\ensuremath{\gamma}{f}_{J})\ifmmode\times\else\texttimes\fi{}\mathcal{B}{(f}_{J}\ensuremath{\rightarrow}h\overline{h})\ensuremath{\sim}1.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ have been set for each of these modes. We compare our results to measurements of other radiative $\ensuremath{\Upsilon}$ decays, to measurements of radiative $J/\ensuremath{\psi}$ decays, and to theoretical predictions.