Lepton flavor violation and collider searches in a type I + II seesaw model

Abstract

Neutrino are massless in the Standard Model. The most popular mechanism to generate neutrino masses are the type I and type II seesaw, where right-handed neutrinos and a scalar triplet are augmented to the Standard Model, respectively. In this work, we discuss a model where a type I + II seesaw mechanism naturally arises via spontaneous symmetry breaking of an enlarged gauge group. Lepton flavor violation is a common feature in such setup and for this reason, we compute the model contribution to the µ → eγ and µ → 3e decays. Moreover, we explore the connection between the neutrino mass ordering and lepton flavor violation in perspective with the LHC, HL-LHC and HE-LHC sensitivities to the doubly charged scalar stemming from the Higgs triplet. Our results explicitly show the importance of searching for signs of lepton flavor violation in collider and muon decays. The conclusion about which probe yields stronger bounds depends strongly on the mass ordering adopted, the absolute neutrino masses and which much decay one considers. In the 1 − 5 TeV mass region of the doubly charged scalar, lepton flavor violation experiments and colliders offer orthogonal and complementary probes. Thus if a signal is observed in one of the two new physics searches, the other will be able to assess whether it stems from a seesaw framework.

Neutrino masses in a two Higgs doublet model with a U(1) gauge symmetry

“…The consideration of different mass hiearchies will not bring much impact to our paper which focuses on the proposition of a new 2HDM model. Anyways, strictly speaking, one should keep in mind that different mass hierarchies are subject to different collider bounds as pointed out [93]. Anyway, if we find ourselves in a situation where both doubly charged scalar and Z fields are observed, our model stands as a potential well motivated environment for them.…”

Charged Lepton Flavor Violation at the High-Energy Colliders: Neutrino Mass Relevant Particles

“…[88][89][90] for classic phenomenological studies and Refs. [91][92][93][94][95][96] for projections of H ±± at future hadron colliders). At the low-energy high-precision frontier, the coupling f αβ is also constrained by the LFV decays α → β γ, α → β γ δ , the electron and muon g − 2, muonium oscillation, and the LEP e + e − → + − data (see e.g., Ref.…”

Flavor symmetries in the Yukawa sector of non-supersymmetric SO(10): numerical fits using renormalization group running

“…This inequality needs to be checked after each fit to make sure that the found parameter values are acceptable. Furthermore, there are experimental bounds on the parameters related to the SU(2) L triplet: v L 1 GeV and M ∆ 1 TeV [58,59]. Finally, the vev v R should be set to M GUT .…”