Elsevier

Nuclear Physics B

Volume 138, Issue 2, 12 June 1978, Pages 285-318
Nuclear Physics B

Determination of the axial vector form factor in the radiative decay of the pion

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Abstract

The branching ratio for the decay π → eνγ has been measured in a counter experiment in which the e+ was detected in a magnetic spectrometer and the γ-ray in a lead-glass hodoscope. The number of observed events is 226.2 ± 22.4. The branching ratio into that part of phase space with electron momentum above 56 MeV/c and the electron-photon opening angle greater than 132° is found to be (5.6 ± 0.7) × 10−8. From the measured branching ratio we determine γ, the ratio of the axial vector tovector form factors. The vector from factor is computed using CVC and the π0 lifetime. For Tπ0 = 0.828 × 10−16 s, γ = 0.44 ± 0.12 or γ = − 2.36 ± 0.12 is obtained. The measurement is compared with several theoretical predictions.

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    Work supported by the US Energy Research and Development Administration under the auspices of the Division of Physical Research.

    Present address: Physics Department, Oregon State University, Corvallis, OR 97331, USA.

    §

    Present address: Physics Department, Chiengmai University, Cheingmai, Thailand.

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