W e determine the mass width o f the meson by applying the S-matrix formalism t o the reaction e+ei n+n-in the timelike region. W e obtain M p = (757.5 f 1.5) MeV and rp = (142.5 * 3.5) MeV, which are significantly smaller than the values quoted by the Particle Data Group. These values are almost independent o f the specific form used t o model the background. PACS number(s): 14.40.Cs, 11.55.Bq. 13.40.Gp, 13.65.-ti

We determine the mass and width of the ∆ ++ (∆ 0 ) resonance from data on π + p (π − p) scattering both, in the pole of the S-matrix and conventionalBreit-Wigner approaches to the scattering amplitude. We provide a simple formula that relates the two definitions for the parameters of the ∆. Isospin

Based on the S-matrix approach, we introduce a modified formula for the π ± electromagnetic form factor which describes very well the experimental data in the energy region 2m π ≤ √ s ≤ 1.1 GeV. Using the CVC hypothesis we predict B(τ − → π − π 0 ν τ ) = (24.75 ± 0.38)%, in excellent agreement with recent experiments.