Preserving local gauge invariance with t-channel Regge exchange.

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 slate on the Regge trajectory. To illustrate the procedure, modifications necessary for the process γ + p → K+ Σ+10 are discussed in some detail. We also provide the general expression for the contact current for an arbitrary reaction. [ABSTRACT FROM AUTHOR]