New Limit of theG-Parity Irregular Weak Nucleon Current Disclosed inβ-Ray Angular Distributions from Spin AlignedB12andN12

The angular distributions of $\beta$ rays from spin aligned ${}_{}{}^{12}{}_{}{}^{}B$ and ${}_{}{}^{12}{}_{}{}^{}N$ were precisely remeasured using a further refined spin-manipulation technique. Our old data have also been recorrected for precisely determined systematic corrections. A nonzero $G$-parity violating induced tensor form factor $f_T$ has been concluded as ${2Mf}_T{/f}_A=+0.22\mathrm{}\pm 0.05\left(\mathrm{stat}\right)\pm 0.15\left(\mathrm{syst}\right)\pm 0.05(\mathrm{theor}.\mathrm{})$. In this result the asymmetry in the axial charges due to the binding-energy difference of the transforming nucleons is taken into account.