We report on a study of exclusive radiative decays of the ${\rm Y}(1S)$ resonance into the final states $\gamma {\pi }^0{\pi }^0$, $\gamma \eta \eta$ and $\gamma {\pi }^0\eta$, using $1.13{\mathrm{fb}}^{-1}$ of ${\mathrm{e}}^{+}{\mathrm{e}}^{-}$ annihilation data collected at $\sqrt{s}=9.46\mathrm{GeV}$ with the CLEO III detector operating at the Cornell Electron Storage Ring. In the channel $\gamma {\pi }^0{\pi }^0$, we measure the branching ratio for the decay mode ${\rm Y}(1S)\to \gamma f_2(1270)$ to be $(10.5\pm 1.6(\mathrm{stat}{)}_{-1.8}^{+1.9}(\mathrm{syst}))\times {10}^{-5}$. We place upper limits on the product branching ratios for the isoscalar resonances $f_0(1500)$ and $f_0(1710)$ for the ${\pi }^0{\pi }^0$ and $\eta \eta$ decay channels. We also set an upper limit on the ${\rm Y}(1S)$ radiative decay into ${\pi }^0\eta$.

• Received 28 November 2005

DOI:https://doi.org/10.1103/PhysRevD.75.072001