Model-independent definition and determination of electromagnetic formfactors and multipole moments

A theoretical method for the systematic definition and determination of Cartesian and spherical electromagnetic (onshell) formfactors and multipole moments for particles or composite systems from electromagnetic Breit-frame current distributions is presented. The method presented is free of sign ambiguities and is not based on the underlying analytical substructure of the electromagnetic current distributions. By construction the method contains all higher order momentum derivative terms within the definition of electromagnetic formfactors and multipole moments, which are not taken into account in a lot of existing theoretical calculations.