The Synthesis Company of San Francisco Mountain Logo

Abstract

The decay modes of the ${\ensuremath{\eta}}^{0}$ meson have been investigated in the Lawrence Radiation Laboratory 72-in. hydrogen bubble chamber. The $\ensuremath{\eta}$'s were produced in the reaction ${\ensuremath{\pi}}^{+}+p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}+p+\ensuremath{\eta}$ at 1225 and 1275 $\frac{\mathrm{MeV}}{c}$ and were studied by analysis of all four-prong and $\mathrm{t}\mathrm{w}\mathrm{o}\ensuremath{-}\mathrm{p}\mathrm{r}\mathrm{o}\mathrm{n}\mathrm{g}+\ensuremath{\gamma}$ events. There appears to be a discrepancy in the measured branching ratio $R=\frac{{\ensuremath{\Gamma}}_{\ensuremath{\eta}}(000)}{{\ensuremath{\Gamma}}_{\ensuremath{\eta}}(+\ensuremath{-}0)}$ as compared with theoretical predictions based on various models relating $R$ to the spectrum of ${{T}_{\ensuremath{\pi}}}^{0} \mathrm{in} {\ensuremath{\eta}}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$. The theoretical predictions calculated from the observed spectrum are uniformly higher than the observed value $R=0.90\ifmmode\pm\else\textpm\fi{}0.24$. For the Brown and Singer theory of a $T=0$, $S=0$ dipion resonance, we find ${m}_{\ensuremath{\sigma}}={{407}_{\ensuremath{-}12}}^{+25}$ MeV, $\ensuremath{\Gamma}=117\ifmmode\pm\else\textpm\fi{}15$ MeV, $R(\mathrm{predicted})=1.49\ifmmode\pm\else\textpm\fi{}0.07$. The fit to the linear matrix-element expansion, $a=\ensuremath{-}0.41\ifmmode\pm\else\textpm\fi{}0.06$, predicts $R=1.63\ifmmode\pm\else\textpm\fi{}0.02$ (the amplitude $f=1+ay$ where $y=\frac{2 {T}_{{\ensuremath{\pi}}^{0}}}{{T}_{{\ensuremath{\pi}}^{0}max}\ensuremath{-}1}$). A fit may be obtained to both the spectrum and the branching ratio with an amplitude $f=(1\ensuremath{-}0.41y){e}^{1.6iy}$, indicating that, although the magnitude of $f$ is essentially smooth, a rapid variation in phase seems to be required to fit the branching ratio.

Decays of theηMeson

Citations Over TimeTop 10% of 1965 papers

Abstract

Related Papers