Rho - Omega Mixing and the Pion Form Factor in the Time - like Region

We determine the magnitude, phase, and s-dependence of ρ-ω " mixing " in the pion form factor in the time-like region through fits to e + e − → π + π − data. The associated systematic errors in these quantities, arising from the functional form used to fit the ρ resonance, are small. The systematic errors in the ρ mass and width, however, are larger than previously estimated.