Measurement of the Correlation between Nuclear Alignment and Electron Direction in <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mmultiscripts><mrow><mi mathvariant="normal">B</mi></mrow><mprescripts></mprescripts><mrow></mrow><mrow><mn>12</mn></mrow><mrow></mrow><mrow></mrow></mmultiscripts></mrow></math></span> Decay as a Direct Search for the Second-Class Axial-Vector Current

P. Lebrun; Ph. Deschepper; L. Grenacs; J. Lehmann; C. Leroy; L. Palffy; A. Possoz; A. Maio

doi:10.1103/PhysRevLett.40.302

Measurement of the Correlation between Nuclear Alignment and Electron Direction in ${}^{12}B$ Decay as a Direct Search for the Second-Class Axial-Vector Current

P. Lebrun, Ph. Deschepper, L. Grenacs, J. Lehmann, C. Leroy, L. Palffy, A. Possoz, and A. Maio

Phys. Rev. Lett. 40, 302 – Published 30 January 1978

Abstract

The alignment correlation term $A α_{-} E P_{2} (cos θ)$ has been measured in the $β^{-}$ decay ${}^{12}B$ → ${}^{12}C$ (g.s.) by a novel technique. The result, $α_{-} (E_{0}) = - \frac{(0.1 \pm 0.2)}{GeV}$ , indicates that the conserved vector current weak-magnetism form factor, $F_{M}$ , is essentially compensated here by the weak electricity (induced tensor) form factor $F_{E}$ . Using the decomposition of $F_{E} = {F_{E}}^{(1)} + {F_{E}}^{(2)}$ into first- and second-class parts, as well as a reliable estimate of ${F_{E}}^{(1)}$ , we conclude that ${F_{E}}^{(2)}$ is small compared to $F_{M}$ , and compatible with zero.