Instanton contribution to scalar charmonium and glueball decays
  We study instanton contributions to hadronic decays of the scalar glueball, the pseudoscalar charmonium state $\eta_c$, and the scalar charmonium state $\chi_c$. Hadronic decays of the $\eta_c$ are of particular interest. The three main decay channels are $K\bar{K}\pi$, $\eta\pi\pi$ and $\eta'\pi\pi$, each with an unusually large branching ratio $\sim 5%$. On the quark level, all three decays correspond to an instanton type vertex $(\bar{c}c)(\bar{s}s)(\bar{d}d)(\bar{u}u)$. We show that the total decay rate into three pseudoscalar mesons can be reproduced using an instanton size distribution consistent with phenomenology and lattice results. Instantons correctly reproduce the ratio $B(\pi\pi\eta)/B(\pi\pi\eta')$ but over-predict the ratio $B(K\bar{K}\pi)/B(\pi\pi\eta(\eta'))$. We consider the role of scalar resonances and suggest that the decay mechanism can be studied by measuring the angular distribution of decay products. 
Valeriu Zetocha (SUNY Stony Brook) and Thomas Schaefer (SUNY Stony   Brook and RIKEN BNL)