Observables for electro-scattering on targets with arbitrary spin

We developed a new algorithm that exhausts all independent operators that can appear in the relativistic scattering amplitudes associated with electromagnetic observables based on the Weinberg formalism to construct fields with arbitrary spin. The new construction offers advantages over existing methods for systematically studying the structure of hadrons and nuclei. Since the construction is based on fields containing minimal degrees of freedom, no subsidiary conditions are needed, and kinematic singularities are absent in amplitudes. Furthermore, it provides a clear physical interpretation of the different non-perturbative distributions entering the decomposition of amplitudes.

Investigating the richer internal structure of higher spin targets can provide insights into the complex underlying dynamics. In this regard, we outline general features that our method exhibits for an arbitrary spin, both for the instant and light-front forms of dynamics. Focusing on spin-1 targets, we apply this method to describe semi-inclusive deep inelastic scattering and deeply virtual Compton scattering on the deuteron, which forms an essential part of the research program at US accelerator facilities (Jefferson Lab and the Electron-Ion Collider).