The width difference of $\rho^{\pm}-\rho^0$ vector mesons and Final State Radiation terms in the $e^+e^-\to \pi^+\pi^-$ cross section are important inputs to evaluate the isospin breaking corrections in the dominant hadronic vacuum polarization contributions to the muon $g-2$, when using $\tau$ lepton data. So far, their contribution have been computed in sQED. Here, we compute the radiative corrections to $\rho \to \pi\pi$ decays, aiming to estimate the width difference of charged and neutral rho mesons, considering the electromagnetic structure of charged mesons and the full Lorentz structure of the electromagnetic vertices. We re-evaluate the width difference of $\rho^{\pm}-\rho^0$ vector mesons and calculate the structure-dependent contributions to Final State Radiation terms in the $e^+e^-\to \pi^+\pi^-$ cross section. Important consequences on muon g-2 prediction are drawn.

toledo@fisica.unam.mx

Genaro Toledo