Abstract
The first measurement of the elementary process is reported. A photon pair spectrometer was used to measure the partial branching ratio for photons of . The value of the weak pseudoscalar coupling constant determined from the partial branching ratio is , where the first error is the quadrature sum of statistical and systematic uncertainties and the second error is due to the uncertainty in , the decay rate of the ortho to para molecule. This value of is times the prediction of partial conservation of axial current and pion-pole dominance.
- Received 19 August 1996
DOI:https://doi.org/10.1103/PhysRevLett.77.4512
©1996 American Physical Society