Experimental measurement of the form factors of the decay K/sub L/0→π+-e-+ν

We have analyzed 25 000 Kₑ₃ decays, reconstructed to the center of mass by measurement of the K_L⁰ momentum from time of flight and measurement of the π and e momenta with a spark-chamber-magnet spectrometer. Using the linear parametrization of the vector form factor f₊(q²)=1+λ₊(q²/m_π²) we find λ₊=0.0270±0.0028. Upper limits for the scalar (f_s) and tensor (f_t) form factors at the 68% confidence level are f_s/f₊<0.04, f_t/f₊<0.23, corresponding to intensity ratios I_s/Iᵥ=0.3% and I_t/Iᵥ<0.4%.