t-channel helicity amplitudes and dispersion inequalities

A new method is proposed for obtaining model-independent dispersion constraints on the differential cross section for the Compton effect on a target with arbitrary spin, based on use of the t-channel helicity amplitudes. The simplicity of this formalism, which is valid for any binary reactions, is demonstrated. The approach satisfies the basic requirements imposed on the formalism for obtaining dispersion inequalities: the differential cross section is expressed in terms of the moduli of the amplitudes, from which the kinematic singularities in the variable ν have been removed