Electromagnetic pion radius and dispersion sum rules

A general set of dispersion sum rules is considered for the pion form factor G(t) in the mixed-modulus phase representation. The connection between the distribution of the G(t) complex zeros and the sizes of dispersion integrals along the cut is stated. Under the assumption that G(t) approximately tsup(α) at large t the following restriction on the asymptotic behaviour of G(t) is obtained: mod(G(t)) >= at-2 (a > 0). Using present experimental data the electromagnetic mean squared radius is evaluated, rsub(π) = 0.71 +- 0.30 fm. (Auth.)