Relevance of various Dirac covariants in hadronic Bethe-Salpeter wave functions in electromagnetic decays of ground state vector mesons

Abstract

In this work we have employed Bethe-Salpeter equation (BSE) under covariant instantaneous ansatz (CIA) to study electromagnetic decays of ground state equal mass vector mesons: $\rho$, $\omega$, $\varphi$, $\psi$ and $Y$ through the process $V\to \gamma \ast \to e^{+}+e^{-}$. We employ the generalized structure of hadron-quark vertex function $\Gamma$ which incorporates various Dirac structures from their complete set order-by-order in powers of inverse of meson mass. The electromagnetic decay constants for the above mesons are calculated using the leading order (LO) and the next-to-leading order (NLO) Dirac structures. The relevance of various Dirac structures in this calculation is studied.

Comments: 20 pages, 3 figures, 4 tables