  The experimental results published by KTeV and the preliminary results from
NA48 concerning the slope of the Kpi scalar form factor suggest a significant
discrepancy with the prediction of the Callan-Treiman low energy theorem once
interpreted within the Standard Model. In this talk, we will show how this
discrepancy could be explained as a first evidence of the direct coupling of
right-handed quarks to W as suggested by certain type of effective electroweak
theories.
