High statistics measurement of the K+→π0e+ν(Ke3) decay formfactors

The decay K+→π0e+ν(Ke3) is studied using in-flight decays detected with ‘OKA’ spectrometer. About 6M events are collected for the analysis. The λ+ slope parameter of the decay formfactor f+(t) in the linear approximation (average slope) is measured: λ+=(29.86±0.2)×10−3. If the quadratic term is added to the parametrization, the result for the linear slope becomes: λ+′=(24.6±0.7)×10−3, the quadratic coefficient in this fit is λ+″=(2.05±0.3)×10−3. Several alternative parametrizations are tried: the Pole fit parameter is found to be: MV=891±3MeV; the parameter of the Dispersive parametrization is measured to be Λ+=(24.6±0.17)×10−3. All the results are very preliminary, the systematics effects are under study.