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arXiv · 2105.11554

Gauge invariance of meson photo- and electroproduction currents revisited

Helmut Haberzettl
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Abstract

An exact expression is derived for the meson production current off the nucleon for real and virtual photons which cleanly separates, in a model-independent manner, a tree-level expression that manifestly preserves local gauge invariance in terms of a generalized Ward-Takahashi identity from transverse final-state-interaction (FSI) terms. As discussed in some detail, this exact formulation is particularly well suited for implementing approximation schemes of exchange-current and FSI contributions (which in practice generally will be necessary) at any level of sophistication without violating local gauge invariance.

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Helmut Haberzettl. 2021-05-24. Gauge invariance of meson photo- and electroproduction currents revisited. https://doi.org/10.1103/physrevd.104.056001

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