Phenomenology of isospin-symmetry breaking with vector mesons

We study the effect of isospin-symmetry breaking in the framework of theextended Linear Sigma Model (eLSM) in vacuum. In this model, several particlesmix with each other at tree level, due to the three non-zero scalar condensates(non-strange, strange, isospin). We resolve these mixings with the help ofvarious field transformations. We compute all possible meson mixings and decaywidths at tree level and perform a $\chi^2$ fit to PDG data. A very good fit isfound if we exclude the (very small $\sim 130$~keV) $\omega\to \pi\pi$ decay.We also investigate the violation of Dashen's theorem.