Light meson spectroscopy and gluonium searches in $\eta_c$ and $\Upsilon(1S)$ decays at BaBar
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 $\Upsilon(nS)\to \pi^+ \pi^- \Upsilon(1S)$, $n=2,3$. We also study the processes $\gamma \gamma \to \eta_c \to \eta^{\prime}K^+K^-$, $\eta^{\prime}\pi^+\pi^-$, and $\eta \pi^+ \pi^-$ using a data sample of 519 $fb^{-1}$ recorded with the BaBar detector at center-of-mass energies at and near the $\Upsilon(nS)$ ($n = 2,3,4$) resonances. A Dalitz plot analysis is performed of $\eta_c$ decays to $\eta^{\prime}K^+K^-$, $\eta^{\prime}\pi^+\pi^-$, and $\eta \pi^+ \pi^-$. A new $a_0(1700)$ resonance is observed in the $\eta \pi^{\pm}$ invariant-mass spectrum from the $\eta_c \to \eta \pi^+ \pi^-$ decay. We compare $\eta_c$ decays to $\eta$ and $\eta^{\prime}$ final states in association with scalar mesons as they relate to the identification of the scalar glueball.