New Limit on Time-Reversal Violation in Beta Decay

We report the results of an improved determination of the triple correlation $D\mathbf{P}\ifmmode\cdot\else\textperiodcentered\fi{}({\mathbf{p}}_{\mathbf{e}}\ifmmode\times\else\texttimes\fi{}{\mathbf{p}}_{\mathbf{v}})$ that can be used to limit possible time-reversal invariance in the beta decay of polarized neutrons and constrain extensions to the standard model. Our result is $D=[-0.96\ifmmode\pm\else\textpm\fi{}1.89(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}1.01(\mathrm{sys})]\ifmmode\times\else\texttimes\fi{}{10}^{-4}$. The corresponding phase between ${g}_{A}$ and ${g}_{V}$ is ${$\phi${}}_{AV}=180.013\ifmmode^\circ\else\textdegree\fi{}\ifmmode\pm\else\textpm\fi{}0.028\ifmmode^\circ\else\textdegree\fi{}$ (68% confidence level). This result represents the most sensitive measurement of $D$ in nuclear $$\beta${}$ decay.