Dispersive analysis of the Primakoff reaction $$\gamma K \rightarrow K \pi $$ γ K → K π

We provide a dispersion-theoretical representation of the reaction amplitudes $$\gamma K\rightarrow K \pi $$ in all charge channels, based on modern pion–kaon P-wave phase shift input. Crossed-channel singularities are fixed from phenomenology as far as possible. We demonstrate how the subtraction constants can be matched to a low-energy theorem and radiative couplings of the $$K^*(892)$$ resonances, thereby providing a model-independent framework for future analyses of high-precision kaon Primakoff data.