## Abstract

The photon energy spectrum from the elementary process [Formula Presented] was measured using a photon pair-spectrometer at the TRIUMF cyclotron. Various sources of backgrounds are discussed in detail and evaluated. From the final spectrum the partial branching ratio [Formula Presented] and the pseudoscalar coupling [Formula Presented] were extracted. The values obtained are [Formula Presented] MeV[Formula Presented] and [Formula Presented], respectively. The first error is the quadrature sum of statistical and systematic errors, while the second error is due to the uncertainty in [Formula Presented] the transition rate of the [Formula Presented] molecule from ortho to para states. This measurement of [Formula Presented] the most precise to date, agrees with all but one of the previous measurements. However it is 1.46 times the value predicted by the partially conserved axial current hypothesis and pion pole dominance.

Original language | English |
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Pages (from-to) | 373-390 |

Number of pages | 18 |

Journal | Physical Review C - Nuclear Physics |

Volume | 57 |

Issue number | 1 |

DOIs | |

State | Published - 1998 |

## ASJC Scopus subject areas

- Nuclear and High Energy Physics