Current Algebra and the Vector Form Factor inKl4Decays

The vector form factor in $K_{l4\mathrm{}}$ decays is expressed in terms of the known decay rate ${\pi }^0\to 2\gamma$, using the technique of current algebra, hard pions and kaon, and the assumption of partially conserved axial-vector current. Its contributions to the various $K_{l4\mathrm{}}$ decay rates are then calculated and its largest value is found to be about 2% that of the axial-vector rate in the case of $K^{+}\to {\pi }^{+}{\pi }^{-}{e}^{+}\nu$ decay.