Two-meson form factors in unitarized chiral perturbation theory

We present a comprehensive analysis of form factors for two light pseudoscalar mesons induced by scalar, vector, and tensor quark operators. The theoretical framework is based on combination unitarized chiral perturbation theory dispersion relations. low-energy constants in are fixed global fit to the available data two-meson scattering phase shifts. Each factor derived from improved iteratively applying relation. This study updates existing results literature explores those that have not been systematically studied previously, particular within theory. also discuss applications these as mandatory inputs phenomena, such semi-leptonic decays $B_s\to \pi^+\pi^-\ell^+\ell^-$ $\tau$ lepton decay $\tau\rightarrow\pi^{-}\pi^{0}\nu_{\tau}$, searches physics beyond Standard Model.