Demonstration of the Need for Meson Exchange Currents in the Beta Decay of <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mmultiscripts><mrow><mi mathvariant="normal">N</mi></mrow><mprescripts></mprescripts><mrow></mrow><mrow><mn>16</mn></mrow><mrow></mrow><mrow></mrow></mmultiscripts></mrow></math></span>(<span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi mathvariant="normal">O</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math></span>)

C. A. Gagliardi; G. T. Garvey; J. R. Wrobel; S. J. Freedman

doi:10.1103/PhysRevLett.48.914

Demonstration of the Need for Meson Exchange Currents in the Beta Decay of ${}^{16}N$ ( $O^{-}$ )

C. A. Gagliardi, G. T. Garvey, J. R. Wrobel, and S. J. Freedman

Phys. Rev. Lett. 48, 914 – Published 5 April 1982

Abstract

The ${}^{16}N (0^{-}, 120 keV) \to {}^{16}O (0^{+}, g . s .) + e^{-} + {\tilde{ν}}_{e}$ beta decay rate is remeasured. The present result, $Λ_{β} = 0.41 \pm 0.06$ $\sec^{- 1}$ , agrees with recent realistic calculations of this rate only when pion exchange currents are included in the axial-vector time component. The impulse approximation underestimates this rate by more than a factor of 3. This result may be combined with the muon capture rate for the inverse reaction to obtain $\frac{g_{P}}{g_{A}} = 10 \pm 2.5$ .