Spacetime evolution of lepton number densities and wave packet-like effects for neutrino flavor and chiral oscillations in quantum field theory

TL;DR

This paper develops a quantum field theory framework for neutrino lepton number densities, applicable across energy regimes, revealing how neutrino mass types can be distinguished despite wave packet decoherence effects.

Contribution

It introduces a novel formulation of lepton family number evolution in quantum field theory that accounts for nonrelativistic and relativistic neutrinos, including wave packet effects.

Findings

Neutrino mass types are distinguishable in the nonrelativistic regime.

Wave packet decoherence effects do not prevent identifying neutrino mass differences.

The approach applies to both Dirac and Majorana neutrinos.

Abstract

We present a formulation of lepton family numbers, based on quantum field theory, for neutrino oscillation phenomenology that can be applied to nonrelativistic and relativistic energies for neutrinos. It is formulated for both types of neutrinos, Dirac and Majorana. The formulation is constructed as the time evolution of a lepton family number density operator. Then, the time evolution of the lepton family number density operator becomes dependent on the mass and new features appear. The expectation value of the density operator is evaluated for the initial state with a Gaussian distribution for the momentum amplitude. This enables us to study wave packet-like decoherence effects. We show in the nonrelativistic regime, the type of neutrino mass are distinguishable even under the presence of wave packet-like decoherence effects.