Generalized structure of hadron–quark vertex function in Bethe–Salpeter framework: applications to leptonic decays of V-mesons

Abstract

We employ the framework of the Bethe–Salpeter equation under a covariant instantaneous ansatz to study the leptonic decays of vector mesons. The structure of the hadron–quark vertex function Γ is generalized to include various Dirac covariants (other than iγ ⋅ ε) from their complete set. They are incorporated in accordance with a naïve power counting rule order-by-order in powers of the inverse of the meson mass. The decay constants for ρ, ω and ϕ mesons are calculated with the incorporation of leading-order covariants.