Masses and couplings of vector mesonsfrom the pion electromagnetic, weak, and transition form factors
Institut für Theoretische Physik, Philosophenweg 16, 69120, Heidelberg, Germany
2 Petersburg Nuclear Physics Institute, 188300, Gatchina, St.-Petersburg, Russia
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We analyze the pion electromagnetic, charged-current, and transition form factors at timelike momentum transfers q, GeV2, using a dispersion approach. We discuss in detail the propagator matrix of the photon-vector meson system and define certain reduced amplitudes, or vertex functions, describing the coupling of this system to final states. We then apply the derived analytic expressions to the analysis of the recent , , and data. We find the reduced amplitudes for the coupling of the photon and vector mesons to two pseudoscalars to be constant, independent of s, in the range considered, indicating a “freezing” of the amplitudes for GeV. The fit to the form factor data leads to the following values of the Breit-Wigner resonance masses MeV, MeV and MeV, where the errors are only statistical.
© Springer-Verlag, 2004