Study of the K−→π0e−ν decay

Abstract The decay K − → π 0 eν has been studied using in-flight decays detected with the “ISTRA+” spectrometer operating in the 25-GeV negative secondary beam of the U-70 PS. About 550K events were collected for the analysis. The λ + parameter of the vector form-factor has been measured: λ + =0.0286±0.0008(stat)±0.0006(syst). The limits on the possible tensor and scalar couplings have been obtained: f T / f + (0)=0.021 +0.064 −0.075 (stat)±0.026(syst); f S / f + (0)=0.002 +0.020 −0.022 (stat)±0.003(syst).