Search for the decayπ0→e+e−

Citations Over TimeTop 13% of 1989 papers

Abstract

The reaction ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}n$ at rest was used as a source of tagged monoenergetic ${\ensuremath{\pi}}^{0}'\mathrm{s}$ in a search for the decay ${\ensuremath{\pi}}^{0}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}$ with the SINDRUM I spectrometer. The measurement resulted in ${B}_{{\ensuremath{\pi}}^{0}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}}\ensuremath{\equiv}\frac{{\ensuremath{\Gamma}}_{{\ensuremath{\pi}}^{0}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}}}{{\ensuremath{\Gamma}}_{{\ensuremath{\pi}}^{0}\ensuremath{\rightarrow}2\ensuremath{\gamma}}}<1.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$ (90% confidence level), consistent with the QED prediction ${B}_{{\ensuremath{\pi}}^{0}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}}=(6.5\ifmmode\pm\else\textpm\fi{}0.5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$. The combined result of two previous measurements, ${B}_{{\ensuremath{\pi}}^{0}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}}=({1.8}_{\ensuremath{-}0.6}^{+0.7})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$, had suggested sizable additional contributions to the decay amplitude. This possibility now seems unlikely.

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