Charge splitting in $\pi N\Delta$ formfactor

Abstract

Experimental data on $\pi N$ scattering in the elastic energy region $W\le 1.45GeV$ are analyzed within the $K$-matrix approach with effective Lagrangians. The charge splitting in ${\delta }_{33}^{++}$ and ${\delta }_{33}^0$ phases obtaned in the phase shift analisys is studed . It is shown that the change in the sign in the energy dependence of the phase difference can be obtained with different formfactors of the ${\Delta }^{++}$ and ${\Delta }^0$ only . This means that ${\Delta }^{++}$ and ${\Delta }^0$ has a different size in $\pi N$ interaction.The underlying nature of the observed phenomena is discussed.