Preserving Local Gauge Invariance with t-Channel Regge Exchange

TL;DR

This paper presents a method to restore local gauge invariance in meson photoproduction processes when using Regge trajectories instead of standard meson exchange, ensuring theoretical consistency.

Contribution

It introduces a contact current construction that cancels gauge-invariance violations caused by Regge exchange in meson production models.

Findings

Successfully restores gauge invariance in Regge-based models.

Provides a general expression for the contact current applicable to various reactions.

Illustrates the method with the $ ext{γ} + p o K^+ + ext{Σ}^{*0}$ process.

Abstract

Considering single-meson photo- and electroproduction off a baryon, it is shown how to restore local gauge invariance that was broken by replacing standard Feynman-type meson exchange in the t-channel by exchange of a Regge trajectory. This is achieved by constructing a contact current whose four-divergence cancels the gauge-invariance-violating contributions resulting from all states above the base state on the Regge trajectory. To illustrate the procedure, modifications necessary for the process $\gamma +p \to K^+ + \Sigma^{*0}$ are discussed in some detail. We also provide the general expression for the contact current for an arbitrary reaction.