Measurement of the invariant-mass spectrum for the two photons from theη→π0γγdecay
Citations Over TimeTop 10% of 2008 papers
Abstract
New results on the rare, doubly radiative decay $\ensuremath{\eta}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}\ensuremath{\gamma}\ensuremath{\gamma}$ have been obtained from a revised analysis of the Crystal Ball experiment performed at the AGS. The analysis yields the first information on the dependence of the decay width, $\ensuremath{\Gamma}(\ensuremath{\eta}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}\ensuremath{\gamma}\ensuremath{\gamma})$, on the two-photon invariant mass squared, ${m}^{2}(\ensuremath{\gamma}\ensuremath{\gamma})$. A re-evaluation of the branching ratio is also made, $\mathit{BR}(\ensuremath{\eta}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}\ensuremath{\gamma}\ensuremath{\gamma})=(2.21\ifmmode\pm\else\textpm\fi{}0.{24}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}0.{47}_{\mathrm{syst}})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$; it implies that the decay width is $\ensuremath{\Gamma}(\ensuremath{\eta}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}\ensuremath{\gamma}\ensuremath{\gamma})=0.285\ifmmode\pm\else\textpm\fi{}0.{031}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}0.{061}_{\mathrm{syst}}$ eV. These results are close to predictions based on chiral perturbation theory with vector-meson dominance.
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