Gauge invariant formulation of 3$\gamma$ decay of particle-antiparticle bound states

TL;DR

This paper develops a gauge invariant framework for calculating the three-photon decay of particle-antiparticle bound states using Dyson-Schwinger and Bethe-Salpeter equations, applicable to various quantum field theoretic models.

Contribution

It introduces a universal, gauge invariant method for three-photon decay amplitudes of bound states, compatible with different QCD-inspired models and effective field theories.

Findings

Constructed gauge invariant three-photon decay amplitude.

Applicable to any quantum field theoretic model of $q\bar{q}$ systems.

Ensures gauge invariance by respecting quantum field theory structure.

Abstract

We construct the gauge invariant three-photon decay amplitude of particle-antiparticle bound states modeled by the Dyson-Schwinger and Bethe-Salpeter equations. Application to the quark-antiquark ($q\bar{q}$) bound states is emphasized. An essential aspect of our formulation is that it applies to any underlying quantum field theoretic model of the $q\bar{q}$ system, and not just to models, like exact QCD, where the quark self-energy $\Sigma$ couples to the electromagnetic field solely via dressed quark propagators. In this way, applications to effective field theories and other QCD motivated models are envisioned. The three-photon decay amplitude is constructed by attaching currents to all possible places in the Feynman diagrams contributing to the dressed quark propagator. The gauge invariance of our construction is thus a direct consequence of respecting the underlying structure of the quantum field theory determining the dynamics. In the resultant expression for the three-photon decay amplitude, all the basic ingredients consisting of the bound state wave function, the final-state interaction $q\bar{q}$ $t$ matrix, the dressed quark propagator, and dressed quark currents, are determined by a universal Bethe-Salpeter kernel.