Possible Experimental Test of Universal Fermi Interaction

The decay modes $K_{e3\mathrm{}}$ and $K_{\mu 3}$ of charged and neutral $K$ particles are discussed with the aim of deriving, in the Feynman-Gell-Mann-Marshak-Sudarshan theory, possible experimental tests of the hypothesis of universal Fermi interaction, which is already apparently contradicted by the present data on the ratio of $\pi \to e+\nu$ to $\pi \to \mu +\nu$. Measurement of the $K_3$ spectra would already provide a test of the hypothesis, and measurements of the polarizations would give further confirmation. Unique forms of the spectra of the charged leptons are predicted on the basis of the universality hypothesis and of particular assumptions.