Massive twistor worldline in electromagnetic fields

TL;DR

This paper explores a twistor-based model for spinning particles interacting with electromagnetic fields, revealing how classical scattering effects and spin interactions can be understood through all-orders-in-spin resummations and the classical eikonal.

Contribution

It introduces a twistor worldline model for spinning particles in electromagnetic fields, demonstrating all-orders-in-spin effects and their relation to the classical eikonal and Newman-Janis shift.

Findings

Computed momentum and spin kicks up to one-loop order.

Resummed spin effects into simple expressions in special kinematic cases.

Linked the classical eikonal to canonical transformations in scattering.

Abstract

We study the (ambi-)twistor model for spinning particles interacting via electromagnetic field, as a toy model for studying classical dynamics of gravitating bodies including effects of both spins to all orders. We compute the momentum kick and spin kick up to one-loop order and show precisely how they are encoded in the classical eikonal. The all-orders-in-spin effects are encoded as a dynamical implementation of the Newman-Janis shift, and we find that the expansion in both spins can be resummed to simple expressions in special kinematic configurations, at least up to one-loop order. We confirm that the classical eikonal can be understood as the generator of canonical transformations that map the in-states of a scattering process to the out-states. We also remark that cut contributions for converting worldline propagators from time-symmetric to retarded amount to the iterated action of the leading eikonal at one-loop order.