Measurement of the angular correlation parameters in theβdecay of polarizedΛhyperons

Abstract

We present our final results from an experimental investigation of the $\beta$ decay of polarized $\Lambda$ hyperons with a large-aperture magnetic spectrometer. Our data sample consists of 544 events. We obtain $A_{\nu }=0.72\mathrm{}\pm 0.12$, $A_e=0.05\mathrm{}\pm 0.12$, and $A_p=-0.47\mathrm{}\pm 0.12$ for the three spin-asymmetry parameters, and $A_{e\nu }=0.07\mathrm{}\pm 0.12$ for the electron-neutrino correlation. The lepton-plane correlation with the $\Lambda$ spin, $D=0.11\mathrm{}\pm 0.20$, is consistent with no violation of time-reversal invariance. Our data yield an axial-vector-to-vector form-factor ratio of $\frac{g_1}{f_1}={0.53}_{-0.09\mathrm{}}^{+0.11\mathrm{}}$. The Cabibbo-model value is $\frac{g_1}{f_1}=0.71\mathrm{}$.