Measurements of the Antineutrino Spin Asymmetry in Beta Decay of the Neutron and Restrictions on the Mass of a Right-Handed Gauge Boson

Abstract

We report a new measurement of the neutron antineutrino spin asymmetry coefficient $B$ in the beta decay of polarized neutrons. Combining results of measurements of the observed asymmetry $PB\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.6617\ifmmode\pm\else\textpm\fi{}0.0044$ with measurements of the neutron beam polarization $P\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(66.88\ifmmode\pm\else\textpm\fi{}0.22)$%, we obtain the value $B\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.9894\ifmmode\pm\else\textpm\fi{}0.0083$. This value implies that the mass of a hypothetical right-handed charged gauge boson in the left-right symmetric model of the weak interaction is greater than $281\mathrm{GeV}/{c}^{2}$ (90% C. L.). This is in agreement with restrictions from muon decay and direct searches for an additional vector boson ${W}^{\ensuremath{'}}$.