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Type I + II Seesaw Model in light of the New Neutrino Oscillation Measurements

Maria Aguilar, Juan Carlos Helo, Toshihiko Ota, Farinaldo S. Queiroz, David Suarez, Amanda Rodríguez

TL;DR

This work analyzes a 3-3-1 gauge-extended model with a scalar sextet that naturally realizes a Type I + Type II seesaw after spontaneous symmetry breaking, addressing neutrino masses under normal ordering. The authors derive neutrino and right-handed neutrino mass structures, explore the gauge sector and EW constraints, and confront collider bounds with lepton flavor-violating (LFV) processes, focusing on μ → eγ and μ → 3e alongside same-sign dilepton searches for a doubly charged scalar. A key finding is the strong dependence of LFV signals on the sextet vev v_s11: for v_s11 ≈ 1 eV, μ → 3e dominates and can impose M_{S^{±±}} > 3 TeV, while for v_s11 ≈ 100 eV, LFV rates are greatly suppressed and collider bounds prevail. The results show that LFV and collider probes are complementary, with current and upcoming μ → 3e experiments potentially providing the strongest tests of this model, independent of precise ∑mν values within current cosmological bounds.

Abstract

Global analysis of neutrino oscillation data slightly favors normal mass ordering. In this work, we investigate an extended scalar sector that naturally gives rise to a type I + II seesaw mechanism after spontaneous symmetry breaking and explore the interplay between collider physics and lepton flavor violation, adopting normal ordering. In particular, we focus on the rare muon decays $μ\rightarrow e γ$ and $μ\rightarrow 3e$ and the same-sign dilepton searches at LHC, a canonical signature of a doubly charged scalar. We conclude that neither the precise value of the sum of the neutrino masses, taken from DESI data that favors $\sum m_ν=0.07$~eV, nor alternative cosmological fits which prefer a more relaxed limit $\sum m_ν=0.1$~eV, significantly changes the theoretical prediction for these rare decays. However, we observe an interesting interplay between collider physics and lepton flavor violation depending on the choices of the vacuum expectation value of the triplet scalar. In particular, we find that $μ\rightarrow 3e$ is more constraining than $μ\rightarrow eγ$, and the $μ\rightarrow 3e$ decay can yield a lower mass limit of $3$~TeV on the doubly charged scalar, surpassing current LHC constraint.

Type I + II Seesaw Model in light of the New Neutrino Oscillation Measurements

TL;DR

This work analyzes a 3-3-1 gauge-extended model with a scalar sextet that naturally realizes a Type I + Type II seesaw after spontaneous symmetry breaking, addressing neutrino masses under normal ordering. The authors derive neutrino and right-handed neutrino mass structures, explore the gauge sector and EW constraints, and confront collider bounds with lepton flavor-violating (LFV) processes, focusing on μ → eγ and μ → 3e alongside same-sign dilepton searches for a doubly charged scalar. A key finding is the strong dependence of LFV signals on the sextet vev v_s11: for v_s11 ≈ 1 eV, μ → 3e dominates and can impose M_{S^{±±}} > 3 TeV, while for v_s11 ≈ 100 eV, LFV rates are greatly suppressed and collider bounds prevail. The results show that LFV and collider probes are complementary, with current and upcoming μ → 3e experiments potentially providing the strongest tests of this model, independent of precise ∑mν values within current cosmological bounds.

Abstract

Global analysis of neutrino oscillation data slightly favors normal mass ordering. In this work, we investigate an extended scalar sector that naturally gives rise to a type I + II seesaw mechanism after spontaneous symmetry breaking and explore the interplay between collider physics and lepton flavor violation, adopting normal ordering. In particular, we focus on the rare muon decays and and the same-sign dilepton searches at LHC, a canonical signature of a doubly charged scalar. We conclude that neither the precise value of the sum of the neutrino masses, taken from DESI data that favors ~eV, nor alternative cosmological fits which prefer a more relaxed limit ~eV, significantly changes the theoretical prediction for these rare decays. However, we observe an interesting interplay between collider physics and lepton flavor violation depending on the choices of the vacuum expectation value of the triplet scalar. In particular, we find that is more constraining than , and the decay can yield a lower mass limit of ~TeV on the doubly charged scalar, surpassing current LHC constraint.

Paper Structure

This paper contains 6 sections, 35 equations, 2 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Model overview
  3. Collider Bounds
  4. Lepton Flavor Violation
  5. Conclusions
  6. Acknowledgments

Figures (2)

  • Figure 1: Branching ratio of the $\mu \rightarrow e \gamma$ decay for $v_{s11}=1\, \text{eV}$ (blue) and $v_{s11}=100\, \text{eV}$ (red). The upper (lower) plot corresponds to the benchmark #1 (#2) for the neutrino oscillation parameters, which is found at Tab. \ref{['tab:numixing']}.
  • Figure 2: Branching ratio of the $\mu \rightarrow 3 e$ decay for $v_{s11}=1\, \text{eV}$ (blue) and $v_{s11}=100\, \text{eV}$ (red) under different neutrino oscillation parameters. The upper (lower) plot corresponds to the benchmark #1 (#2) for the neutrino oscillation parameters, which is given in Tab. \ref{['tab:numixing']}.