Vector form factor of the pion from unitarity and analyticity:: A model-independent approach -: art. no. 093005

We study a model-independent parametrization of the vector pion form factor that arises from the constraints of analyticity and unitarity. Our description should be suitable up to roots similar or equal to1.2 GeV and allows a model-independent determination of the mass of the rho (770) resonance, M-rho=(775.1+/-0.5) MeV. We analyze the experimental data on tau (-) --> pi (-) pi (0)nu (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(mu), and to the line structure constant, alpha (M-Z(2)), is also performed.