Measurement of Γ(Kμ3)/Γ(Ke3) ratio using stopped positive kaons

Abstract The ratio of the K + → π 0 μ + ν ( K μ 3 + ) and K + → π 0 e + ν ( K e 3 + ) decay widths, Γ ( K μ 3 )/ Γ ( K e 3 ), has been measured with stopped positive kaons. K μ 3 + and K e 3 + samples containing 2.4×10 4 and 4.0×10 4 events, respectively, were analyzed. The Γ ( K μ 3 )/ Γ ( K e 3 ) ratio was obtained to be 0.671±0.007(stat.)±0.008(syst.) calculating the detector acceptance by a Monte Carlo simulation. The coefficient of the q 2 dependent term of the f 0 form factor was also determined to be λ 0 =0.019±0.005(stat.)±0.004(syst.) with the assumption of μ – e universality in K l 3 + decay. The agreement of our result with the λ 0 value obtained from K μ 3 + Dalitz plot analyses supports the validity of the μ – e universality.