Υ dipion transitions at energies near the Υ ( 4 S )

Using a $4.19{\mathrm{fb}}^{\mathrm{\ensuremath{-}}1}$ data sample collected with the CLEO II detector at the Cornell Electron Storage Ring, we have searched for dipion transitions between pairs of \ensuremath{\Upsilon} resonances at center of mass energies ${E}_{\mathrm{c}.\mathrm{m}.}=10.58\mathrm{GeV}$ and ${E}_{\mathrm{c}.\mathrm{m}.}=10.52\mathrm{GeV}.$ We obtain the 90% confidence level upper limits $\mathcal{B}(\ensuremath{\Upsilon}(4S)\ensuremath{\rightarrow}\ensuremath{\Upsilon}(2S){\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})l3.9\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ and $\mathcal{B}(\ensuremath{\Upsilon}(4S)\ensuremath{\rightarrow}\ensuremath{\Upsilon}(1S){\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})l1.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}.$ We also observe the transitions $\ensuremath{\Upsilon}(3S)\ensuremath{\rightarrow}\ensuremath{\Upsilon}(1S){\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}},$ $\ensuremath{\Upsilon}(3S)\ensuremath{\rightarrow}\ensuremath{\Upsilon}(2S){\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}},$ and $\ensuremath{\Upsilon}(2S)\ensuremath{\rightarrow}\ensuremath{\Upsilon}(1S){\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}},$ from which we measure the cross sections for the radiative processes ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\Upsilon}(3S)\ensuremath{\gamma}$ and ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\Upsilon}(2S)\ensuremath{\gamma}.$ We obtain ${\ensuremath{\sigma}}_{e\stackrel{\ensuremath{\rightarrow}}{e}\ensuremath{\Upsilon}(3S)\ensuremath{\gamma}}=(17.8\ifmmode\pm\else\textpm\fi{}3.0\ifmmode\pm\else\textpm\fi{}1.7)\mathrm{pb}$ and ${\ensuremath{\sigma}}_{e\stackrel{\ensuremath{\rightarrow}}{e}\ensuremath{\Upsilon}(2S)\ensuremath{\gamma}}=(15.5\ifmmode\pm\else\textpm\fi{}1.3\ifmmode\pm\else\textpm\fi{}1.4)\mathrm{pb}$ at ${E}_{\mathrm{c}.\mathrm{m}.}=10.58\mathrm{GeV},$ and ${\ensuremath{\sigma}}_{e\stackrel{\ensuremath{\rightarrow}}{e}\ensuremath{\Upsilon}(3S)\ensuremath{\gamma}}=(27.3\ifmmode\pm\else\textpm\fi{}5.0\ifmmode\pm\else\textpm\fi{}2.6)\mathrm{pb}$ and ${\ensuremath{\sigma}}_{e\stackrel{\ensuremath{\rightarrow}}{e}\ensuremath{\Upsilon}(2S)\ensuremath{\gamma}}=(16.3\ifmmode\pm\else\textpm\fi{}1.8\ifmmode\pm\else\textpm\fi{}1.5)\mathrm{pb}$ at ${E}_{\mathrm{c}.\mathrm{m}.}=10.52\mathrm{GeV},$ which we compare with theoretical predictions.