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pi+ - pi0 mass difference from the Bethe-Salpeter equation

Masayasu Harada, Masafumi Kurachi, Koichi Yamawaki

hep-pharXiv:hep-ph/0403120

Abstract

In the framework of the Schwinger-Dyson equation and the Bethe-Salpeter equation in the improved ladder approximation, we calculate the pi+ - pi0 mass difference on the same footing as the pion decay constant and the QCD S parameter (or L10) through the difference between the vector current correlator ΠVV and the axial-vector current correlator ΠAA. We find that all the results can be fit to the experimental values for rather large LambdaQCD 700 MeV which reflects the ``scale ambiguity''. By fitting to the calculated data using the pole saturated form of ΠVV - ΠAA, we also derive masses and decay constants of rho meson and a1 meson, which we found are consistent with the experiments rather insensitively to the ``scale ambiguity''.

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