Hadron structure and pion electroproduction at threshold

A current status of the experimental studies of the threshold electroproduction of pions on nucleons is reviewed. The data on separation of the transverse and longitudinal components to the threshold slope of the cross section are emphasized as a main achievement of the recent years. The axial-vector form factor of the nucleon has been determined from the transverse component and proved to have weak model dependence. The axial mass in the dipole fit is found to equal (0.97+-0.06) GeV. An electromagnetic pion radius 1/2(0.45+-0.10) F, has been determined from the longitudinal component. Dependences of the threshold slopes of cross sections on the polarization of a virtual photon and the results for determination of the transverse and longitudinal components for the sum of the π0 and π+ production channels are presented in a graphical form. Comparison of the results of the different methods used demonstrates their consistency