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The vector form factor of the pion from unitarity and analyticity: a model-independent approach

A. Pich·J. Portoles
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Abstract

We study a model-independent parameterization of the vector pion form factor that arises from the constraints of analyticity and unitarity. Our description should be suitable up to sqrt(s) ~ 1.2 GeV and allows a model-independent determination of the mass of the rho(770) resonance, M(rho) = (775.1 +- 0.5) MeV. We analyse the experimental data on tau(-) -> pion(-) pion(0) neutrino(tau), in this framework, and its consequences on the low-energy observables worked out by chiral perturbation theory. An evaluation of the two-pion contribution to the anomalous magnetic moment of the muon, a_muon, and to the fine structure constant, alpha(M(Z)^2), is also performed.

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A. Pich, J. Portoles. 2001-01-17. The vector form factor of the pion from unitarity and analyticity: a model-independent approach. https://doi.org/10.1103/physrevd.63.093005

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