Electromagnetic Pion and Nucleon Form Factors at Positive and Negative $q^2$ Within the Framework of Quark-Gluon Strings Model

Abstract

The electromagnetic form factors of pion and nucleon are considered within the framework of the Quark-Gluon Strings Model, where the dependence of the form factors on $q^2$ is determined by the intercept of a dominant Regge trajectory and Sudakov form factor. The analytical expressions for the form factors found in the time-like region can be directly continued to the space-like region. Good agreement with available experimental data on the pion and magnetic nucleon form factor is obtained at positive as well as negative $q^2$. It is shown that the difference in $F_\pi$ and $G_m$ at positive and negative values of $q^2$ is mainly related to the behavior of the double logarithmic term in the exponent of Sudakov form factor. The model describes also existing data on the Pauli nucleon form factor $F_2$ and the ratio $G_e/G_m$.