Test for descriptions of relativistic spin dynamics by using ultraintense lasers

The relativistic spin operator cannot be uniquely defined within relativistic quantum mechanics. Searching for relativistic equations that describe both the evolution of the spin and its influence on the motion of particles with spin represents a problem with almost centenary history. We develop a self-consistent module for modeling relativistic particles with spin motion into three-dimensional particle-in-cell simulations, where the expression of the spin-induced force can be chosen by various semiclassical models, such as the Frenkel and noncovariant Derbenev-Kondratenko models. Through simulations, we propose a potential experimental scheme for observing and testing theoretical descriptions on relativistic spin dynamics, where ultraintense lasers are used to collide with relativistic electron beams. The basis for the scheme is that different models predict different transverse polarization distributions of the scattered electrons after interactions, which can be measured in experiments.