Neutrino Hierarchies from a Gauge Symmetry

TL;DR

This paper explores how a specific gauge symmetry influences neutrino mass hierarchies and proposes a dark matter candidate arising from symmetry breaking, linking neutrino physics with dark matter phenomenology.

Contribution

It introduces a novel gauge symmetry model that explains neutrino mass hierarchies and predicts a dark matter candidate connected to symmetry breaking and anomaly cancellation.

Findings

Normal hierarchy arises from L_e symmetry

Inverted hierarchy requires a Z_2 symmetry

Dark matter relic abundance matches resonance conditions

Abstract

We consider the phenomenology of the gauged abelian symmetry B + 3 (L_e - L_mu - L_tau). Right-handed neutrinos necessary to cancel triangle anomalies are used in a type-I seesaw scheme to create active neutrino masses. Breaking the B + 3 (L_e - L_mu - L_tau) symmetry spontaneously below the seesaw scale generates low energy neutrino mass matrices with the approximate symmetries L_e (leading to normal hierarchy) or L_e - L_mu - L_tau (inverted hierarchy). For the latter we need to introduce a Z_2 symmetry which decouples one of the right-handed neutrinos. If exact, this Z_2 leads to a Majorana dark matter candidate that interacts with the Standard Model via the Z' and a scalar s originating from spontaneous breaking of the new symmetry. The measured relic abundance of the dark matter particle can be obtained around the scalar and Z' resonances, while direct detection experiments are mainly sensitive to scalar exchange, which is induced by mass mixing of s with the standard Higgs.