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

The ratio of the K+ --> pi (0)mu (+)nu (K-mu3(+)) and K+ --> pi (0)e(+)nu (K-e3(+)) decay widths, Gamma (K-mu3)/Gamma (K-e3), has been measured with stopped positive kaons. K-mu3(+) and K-e3(+) samples containing 2.4 x 10(4) and 4.0 x 10(4) events, respectively, were analyzed. The Gamma (K-mu3)/Gamma (K-e3) 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 lambda (0) = 0.019 +/- 0.005(stat.) +/- 0.004(syst.) with the assumption of mu -e universality in K-l3(+) decay. The agreement of our result with the lambda (0) value obtained from K-mu3(+) Dalitz plot analyses supports the validity of the mu -e universality. (C) 2001 Elsevier Science B.V. All rights reserved.