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Dirac Neutrinos and Gauged Lepton Number

A. E. Cárcamo Hernández, Andrés Enríquez, Sergey Kovalenko, Eduardo Peinado, Carlos A. Vaquera-Araujo

TL;DR

This work constructs a scotogenic model with gauged lepton number U(1)_L that is spontaneously broken by Delta L=3 to a remnant Z6, guaranteeing radiative Dirac neutrino masses and stabilizing a dark matter candidate. The model extends the SM with vector-like leptons and inert scalars, enabling a one-loop Dirac neutrino mass through mediators S_i and a Z6-protected dark sector; a leptophilic Z' with mass M_Z'^2 = 9 g_L^2 w^2 arises and does not couple to quarks. The authors analyze scalar and gauge sectors, DM relic abundance with Omega h = 0.120 +/- 0.001 and direct-detection bounds, and charged lepton flavor violation in mu -> e gamma and mu -> 3e, finding viable parameter space and predictions within current or upcoming experimental reach. This framework links neutrino mass generation to dark matter stability via a natural remnant discrete gauge symmetry, offering a testable BSM scenario with concrete collider and LFV phenomenology.

Abstract

We propose the first scotogenic neutrino mass model with gauged lepton number $U(1)_L$, which is spontaneously broken by three units $ΔL=3$ down to a residual discrete gauge symmetry $\mathbb{Z}_6$. The latter guarantees that neutrinos acquire tiny Dirac masses via a one-loop scotogenic mechanism, simultaneously stabilizing the lightest electrically neutral particle with non-trivial charge under the preserved $\mathbb{Z}_6$ symmetry. In our model there is a scalar particle identified as weakly interacting massive particle dark matter (DM) candidate. We analyzed its compatibility with the existing data on direct DM detection experiments and the DM relic abundance. We also address charged lepton flavor violating decays in our model and find that their predicted rates are within the reach of current experimental sensitivity.

Dirac Neutrinos and Gauged Lepton Number

TL;DR

This work constructs a scotogenic model with gauged lepton number U(1)_L that is spontaneously broken by Delta L=3 to a remnant Z6, guaranteeing radiative Dirac neutrino masses and stabilizing a dark matter candidate. The model extends the SM with vector-like leptons and inert scalars, enabling a one-loop Dirac neutrino mass through mediators S_i and a Z6-protected dark sector; a leptophilic Z' with mass M_Z'^2 = 9 g_L^2 w^2 arises and does not couple to quarks. The authors analyze scalar and gauge sectors, DM relic abundance with Omega h = 0.120 +/- 0.001 and direct-detection bounds, and charged lepton flavor violation in mu -> e gamma and mu -> 3e, finding viable parameter space and predictions within current or upcoming experimental reach. This framework links neutrino mass generation to dark matter stability via a natural remnant discrete gauge symmetry, offering a testable BSM scenario with concrete collider and LFV phenomenology.

Abstract

We propose the first scotogenic neutrino mass model with gauged lepton number , which is spontaneously broken by three units down to a residual discrete gauge symmetry . The latter guarantees that neutrinos acquire tiny Dirac masses via a one-loop scotogenic mechanism, simultaneously stabilizing the lightest electrically neutral particle with non-trivial charge under the preserved symmetry. In our model there is a scalar particle identified as weakly interacting massive particle dark matter (DM) candidate. We analyzed its compatibility with the existing data on direct DM detection experiments and the DM relic abundance. We also address charged lepton flavor violating decays in our model and find that their predicted rates are within the reach of current experimental sensitivity.
Paper Structure (10 sections, 36 equations, 4 figures, 1 table)

This paper contains 10 sections, 36 equations, 4 figures, 1 table.

Table of Contents

  1. Introduction
  2. The Model
  3. Boson Sector
  4. Scalars
  5. Gauge Bosons
  6. Scotogenic Neutrino Mases
  7. Dark Matter
  8. Charged lepton flavor violation
  9. Summary and conclusions
  10. Anomaly Cancellation

Figures (4)

  • Figure 1: One-loop diagram for neutrino masses.
  • Figure 2: Dark matter direct detection and relic abundance bounds. Each point represents a set of parameters that reproduces the correct relic abundance measured by PLANCK Planck:2018vyg. Current limits from the LUX-ZEPLIN collaboration LZ:2024zvo are shown, together with future experiment projected sensitivities Billard:2021uygDarkSide-20k:2017zygSchumann:2015cpa.
  • Figure 3: Correlations between $Br\left(\mu \rightarrow e\gamma\right)$ and ${\rm Tr}\left(zz^{\dagger }\right)$ as well as between $Br\left(\mu\rightarrow 3e\right)$ and $Br\left(\mu \rightarrow e\gamma\right)$. For the definitions see Sec. \ref{['Sect:cLFV']}.
  • Figure 4: Correlation between $m_{\eta^\pm}$ and $\mathrm{Tr}\left(zz^{\dagger }\right)$ for different values of the branching ratio of $\mu \rightarrow e\gamma$.