The Standard Model of particle physics with Diracian neutrino sector

TL;DR

This paper introduces a Diracian neutrino model extending the Standard Model, which offers a better fit to data, predicts feeble neutrinoless double beta decay, and supports sterile neutrino explanations for ultra-high-energy cosmic events.

Contribution

It proposes a Diracian limit of the neutrino sector that enhances the Standard Model with new parameters and phases, improving data description and phenomenological implications.

Findings

Degenerate neutrino masses in the Diracian limit

Enhanced data fit with additional phases and parameters

Supports sterile neutrino interpretation of ANITA events

Abstract

The minimally extended standard model of particle physics contains three right handed or sterile neutrinos, coupled to the active ones by a Dirac mass matrix and mutually by a Majorana mass matrix. In the pseudo-Dirac case, the Majorana terms are small and maximal mixing of active and sterile states occurs, which is generally excluded for solar neutrinos. In a "Diracian" limit, the physical masses become pairwise degenerate and the neutrinos attain a Dirac signature. Members of a pair do not oscillate mutually so that their mixing can be undone, and the standard neutrino model follows as a limit. While two Majorana phases become physical Dirac phases and three extra mass parameters occur, a better description of data is offered. Oscillation problems are worked out in vacuum and in matter. With lepton number -1 assigned to the sterile neutrinos, the model still violates lepton number conservation and allows very feeble neutrinoless double beta decay. It supports a sterile neutrino interpretation of Earth-traversing ultra high energy events detected by ANITA.