Study of $\Upsilon(1S)$ Radiative Decays to $\gamma \pi^+ \pi^-$ and $\gamma K^+ K^-$

Abstract

We study the $\Upsilon(1S)$ radiative decays to $\gamma \pi^+ \pi^-$ and $\gamma K^+ K^-$ using data recorded with the BaBar detector operating at the SLAC PEP-II asymmetric-energy $e^+ e^-$ collider at center-of-mass energies at the $\Upsilon(2S)$ and $\Upsilon(3S)$ resonances. The $\Upsilon(1S)$ resonance is reconstructed from the decay $\Upsilon(nS)\to \pi^+ \pi^- \Upsilon(1S)$, $n=2,3$. Branching fraction measurements and spin-parity analyses of $\Upsilon(1S)$ radiative decays are reported for the I=0 $S$-wave and $f_2(1270)$ resonances in the $\pi^+ \pi^-$ mass spectrum, the $f_2'(1525)$ and $f_0(1500)$ in the $ K^+ K^-$ mass spectrum, and the $f_0(1710)$ in both.