Electromagnetic form Factors of the Proton in the Time Like Region

Abstract

From the simple fact that a proton interacts with, say, a π meson, on the basis of pure theoretical arguments, we should expect the proton to have at least some kind of electromagnetic structure. In fact, the theory of the strong interactions, even in the very crude form it has been formulated in early times, indicates that the nucleon is surrounded by a mesonic field that has an extension with a radius of the order of the π meson Compton wavelength. This mesonic field is supposed to carry a charge distribution. Thus, in order to have a deeper insight in the mechanism of the strong interactions it seems worthwhile to investigate experimentally the electromagnetic properties of the nucleons. This is why one of the significant programs in high energy physics has been the systematic study of the electron-proton elastic scattering initiated by Hofstadter (1955, 1965)1. The explanation of these experiments has been an outstanding problem in the theory of strong interactions and has led to many new and interesting ideas2.