Report of the Topical Group on Neutrino Properties for Snowmass 2021

TL;DR

This paper reviews the current understanding and open questions regarding neutrino properties, including mass, nature, and electromagnetic characteristics, highlighting areas for future research in neutrino physics.

Contribution

It provides a comprehensive overview of neutrino properties not covered by other groups, emphasizing unresolved issues and potential experimental approaches.

Findings

Neutrino masses remain undetermined.

The Dirac or Majorana nature of neutrinos is still unknown.

Neutrino electromagnetic properties are largely unexplored.

Abstract

Neutrinos are the most elusive among the known elementary particles, because of their feeble interactions with ordinary matter. They are also the most mysterious, because of their tiny masses that suggest a novel mass generating mechanism, their unknown Dirac or Majorana nature, and their big quantum mixing leading to large-amplitude flavor oscillations. This Topical Group focuses on neutrino properties that are not directly investigated in other Topical Groups of the Neutrino Frontier: in particular, the absolute value of the neutrino masses, the Dirac or Majorana nature of neutrinos, their electromagnetic properties, their lifetime, and hypothetical exotic properties.