Measurement of the Branching Ratio and Form Factors for the Decay \boldmath $K_L\toπ^{\pm}π^0e^{\mp}ν_e(\barν_e)

Abstract

The $K_L\toπ^{\pm}π^0e^{\mp}ν_e(\barν_e)$ decay was investigated with the NA48 detector at CERN SPS using a beam of long-lived neutral kaons. The branching ratio $Br(K_L\toπ^{\pm}π^0e^{\mp}ν_e(\barν_e))=(5.21\pm 0.07_{stat}\pm 0.09_{syst})\times 10^{-5}$ was fixed from a sample of 5464 events with 62 background events. The form factors $\bar{f}_s$, $\bar{f}_p$, $λ_g$ and $\bar{h}$ were found to be in agreement with previous measurements but with higher accuracy. The coupling parameter of the chiral Lagrangian $L_3=(-4.1\pm 0.2)\times 10^{-3}$ was evaluated from the data.