A new measurement of the (K+ → e+v)(K+ → μ +v) branching ratio

The branching ratio $\text{R = Γ(}\text{K}{}^{\mathrm{+}}\text{→}\text{e}{}^{\mathrm{+}}\text{v)}\text{Γ(}\text{K}{}^{\mathrm{+}}\text{→ μ}{}^{\mathrm{+}}\text{v)}$ has been measured with an improved version of the apparatus described elsewhere. From 404 observed K⁺ → e⁺v decays, R = (2.51 ± 0.15) × 10^?5 was obtained, to be compared with the value predicted for pure axialvector interaction and μ-e-universality, R_theor = 2.57 × 10^?5.