Bounds on right-handed currents from nuclear beta decay.

Abstract

Constraints on right-handed currents are set by the precise comparison of the longitudinal polarizations ${P}_{\mathrm{F}}$ and ${P}_{\mathrm{GT}}$ in Fermi and Gamow-Teller ${\ensuremath{\beta}}^{+}$ decay. Measurements with a new fourfold Bhabha polarimeter gave ${P}_{\mathrm{F}/{P}_{\mathrm{GT}=1.003\ifmmode\pm\else\textpm\fi{}0.004}}$ with use of the matching isotopes $^{26\mathrm{m}}\mathrm{Al}$ and $^{30}\mathrm{P}$. This ratio translates directly into a bound on the product of the mixing angle \ensuremath{\zeta} and mass-squared ratio \ensuremath{\delta} of the left- and right-handed W bosons given by -0.49\ifmmode\times\else\texttimes\fi{}${10}^{3}$1.2 at 90% confidence.