DOI 10.1007/s100520000308
Dispersive and chiral symmetry
constraints
on the light meson form factors
I. Caprini
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
Abstract
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
