Pion off-shell form factors

In the paper, the electromagnetic off-shell pion form factors in the Bethe-Salpeter formalism with a separable kernel are considered. Different types of vertex functions of a pion are investigated. The separable kernel of the quark-antiquark interaction is used to obtain an analytical solution of the equation. The pion constants and the form factors on both the on-shell and off-shell surfaces are calculated. The differential cross section of the reaction $^1H(e,e' \pi^ +) n$ is also calculated in the paper. All the obtained results are compared with experimental data. The fulfillment of the Ward-Takahashi identity for the off-shell form factors $F_1(Q^2,t)$ and $F_2(Q^2,t)$ of a pion is verified.