Consistent interactions for high-spin fermion fields

TL;DR

This paper develops a general framework for consistent interactions of high-spin fermion fields, addressing unphysical degrees of freedom and proposing a novel form factor to improve physical predictions in hadronic processes.

Contribution

It introduces the most general consistent interaction structure for high-spin fermions and proposes a spin-dependent form factor to suppress unphysical artifacts.

Findings

Interaction momentum dependence increases with spin.

Unphysical structures appear in cross sections with standard form factors.

A new spin-dependent form factor effectively suppresses artifacts.

Abstract

We address the issue of consistent interactions for off-shell fermion fields of arbitrary spin. These interactions play a crucial role in the quantum hadrodynamical description of high-spin baryon resonances in hadronic processes. The Rarita-Schwinger description of high-spin fermion fields involves unphysical degrees of freedom, associated with their lower-spin content. These enter the interaction if not eliminated outright. The invariance condition of the interaction under the unconstrained Rarita-Schwinger gauge removes the lower-spin content of the fermion propagator and leads to a consistent description of the interaction. We develop the most general, consistent interaction structure for high-spin fermions. We find that the power of the momentum dependence of a consistent interaction rises with the spin of the fermion field. This leads to unphysical structures in the energy dependence of the computed cross sections when the short-distance physics is cut off with standard hadronic form factors. A novel, spin-dependent hadronic form factor is proposed that suppresses the unphysical artifacts.