Invariant amplitudes for coherent electromagnetic pseudoscalar production from a spin-one target

A set of 13 linearly independent invariant amplitudes for the electromagnet ic production of a pseudoscalar particle from a spin-one particle is derive d which respect Lorentz and gauge invariance. The T-matrix can be represent ed by a linear superposition of these amplitudes with invariant functions a s coefficients, which depend on the Mandelstam variables only. Their explic it form is determined by the underlying dynamics. Nine of these amplitudes are purely transverse and describe photoproduction. The remaining four appe ar in electroproduction in addition, describing charge and longitudinal cur rent contributions. Furthermore, a reduction of these amplitudes to operato rs acting in non-relativistic spin space is given.