Preprint IHEP 2004-12,  hep-ex/0404030

Authors: O.P.Yushchenko, et al.
"High statistic measurement of the K- -> pi0 e- nu decay form-factors"


        Abstract

  The decay K- -> pi0 e- nu is studied using in-flight decays detected with 
the ISTRA+ spectrometer. About 920K events are collected for the analysis. 
The lambda+ slope parameter of the decay form-factor f+(t) in the linear 
approximation (average slope) is measured: 
lambda+(lin)= 0.02774 +- 0.00047(stat) +- 0.00032(syst). 
The quadratic contribution to the form-factor was estimated to be 
lambda'+ = 0.00084 +- 0.00027(stat) +- 0.00031(syst). 
The linear slope, which has a meaning of df+(t)/dt|_{t=0} for this fit, is 
lambda+ = 0.02324 +- 0.00152(stat) +- 0.00032(syst). 
The limits on possible tensor and scalar couplings are derived: 
f_{T}/f_{+}(0)=-0.012 +- 0.021(stat) +- 0.011$(syst), 
f_{S}/f_{+}(0)=-0.0037^{+0.0066}_{-0.0056}(stat) +- 0.0041(syst).