A New Spin on Neutrino Quantum Kinetics

TL;DR

This paper explores the physical origin and implications of a coherent spin-flip term in neutrino quantum kinetic equations, revealing its dependence on neutrino mass and Majorana phases in anisotropic environments.

Contribution

It provides explicit expressions for the quantum kinetic equations including the spin-flip term and analyzes its physical origin and dependence on neutrino properties.

Findings

Coherent spin-flip term arises in anisotropic environments.

Spin transformation depends on neutrino mass and Majorana phases.

Explicit QKEs are derived for a two-flavor spherical model.

Abstract

Recent studies have demonstrated that in anisotropic environments a coherent spin-flip term arises in the Quantum Kinetic Equations (QKEs) which govern the evolution of neutrino flavor and spin in hot and dense media. This term can mediate neutrino-antineutrino transformation for Majorana neutrinos and active-sterile transformation for Dirac neutrinos. We discuss the physical origin of the coherent spin-flip term and provide explicit expressions for the QKEs in a two-flavor model with spherical geometry. In this context, we demonstrate that coherent neutrino spin transformation depends on the absolute neutrino mass and Majorana phases.