The energy distribution for left- and right-handed ${\nu }_e$ from the decay of unpolarized ${\mu }^{+}$ has been calculated on the basis of the most general four-fermion interaction. The left-handed ${\nu }_e$ can be detected by the reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({\nu }_e,e^{-}){}_{}{}^{12}{}_{}{}^{}\mathrm{N} (\mathrm{g}.\mathrm{s}.\mathrm{})$. A measurement of the total rate with an error of < 5% will improve present limits on the scalar coupling $g_{\mathrm{LL}}^S$. The energy distribution for a left-handed ${\nu }_e$ depends on the parameter ${\omega }_L$ which corresponds to the Michel parameter $\varrho$ of the electron energy spectrum from muon decay. The standard model predicts ${\omega }_L=0\mathrm{}$. The new parameter ${\omega }_L$ can be determined with a precision of $\Delta {\omega }_L=0.026\mathrm{}$ for 100 events corresponding to $|g_{\mathrm{RL}}^S+2\mathrm{}{g}_{\mathrm{RL}}^T|\leqq 0.37$, where $g_{\mathrm{RL}}^S$ and $g_{\mathrm{RL}}^T$ represent scalar and tensor interactions with left-handed ${\nu }_e$ and right-handed ${\overline{\nu }}_{\mu }$.

Close

PrevNext

View figure in article