Dispersive and chiral symmetry
on the light meson form factors
National Institute of Physics and Nuclear Engineering,
POB MG 6, 76900 Bucharest, Romania
Received: 16 July 1999 / Published online: 6 March 2000 - © Springer-Verlag 2000
The form factors of the light pseudoscalar mesons are investigated in a dispersive formalism based on hadronic unitarity, analyticity and the OPE expansion of the QCD Green functions. We propose generalizations of the original mathematical techniques, suitable for including additional low energy information provided by experiment or Chiral Perturbation Theory (CHPT). The simultaneous treatment of the electroweak form factors of the and K mesons allows us to test the consistency with QCD of a low energy CHPT theorem. By applying the formalism to the pion electromagnetic form factor, we derive quite strong constraints on the higher Taylor coefficients at zero momentum, using information about the phase and the modulus of the form factor along a part of the unitarity cut.
Copyright Società Italiana di Fisica, Springer-Verlag 2000