Spin polarization from nucleon-nucleon scatterings in intermediate-energy heavy-ion collisions

TL;DR

This paper introduces a new mechanism for generating spin polarization in intermediate-energy heavy-ion collisions, based on nucleon-nucleon scatterings, which could explain observed polarization phenomena.

Contribution

The study proposes incorporating spin changes in nucleon-nucleon scatterings into transport models, revealing a significant polarization effect in heavy-ion collisions.

Findings

Approximately 1-2% spin polarization generated

Mechanism consistent with angular momentum conservation

Potential explanation for experimental polarization observations

Abstract

We propose a new mechanism of generating spin polarization in heavy-ion collisions dominated by nucleon degree of freedom. By incorporating the spin change in nucleon-nucleon scatterings based on the phase shift data together with the constraint of rigorous angular momentum conservation and Pauli blocking, we illustrate through a Boltzmann-Uehling-Uhlenbeck transport model that appreciable spin polarization (about $1 \sim 2\%$) can be generated in intermediate-energy heavy-ion collisions. This mechanism, together with the nuclear spin-orbit potential, may help to understand the spin polarization in few-GeV heavy-ion collisions dominated by nucleon degree of freedom.