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

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.

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Measurement of the Correlation between Nuclear Alignment and Electron Direction inB12Decay as a Direct Search for the Second-Class Axial-Vector Current