Neutrino mass, dark matter and anomalous magnetic moment of muon in a U 1 L μ − L τ $$ \mathrm{U}{(1)}_L{{}_{{}_{\mu}}}_{-}{{}_L}_{{}_{\tau }} $$ model

Abstract

The observation of neutrino masses, mixing and the existence of dark matter are amongst the most important signatures of physics beyond the Standard Model (SM). In this paper, we propose to extend the SM by a local L µ −L τ gauge symmetry, two additional complex scalars and three right-handed neutrinos. The L µ − L τ gauge symmetry is broken spontaneously when one of the scalars acquires a vacuum expectation value. The L µ − L τ gauge symmetry is known to be anomaly free and can explain the beyond SM measurement of the anomalous muon (g − 2) through additional contribution arising from the extra Z µτ mediated diagram. Small neutrino masses are explained naturally through the Type-I seesaw mechanism, while the mixing angles are predicted to be in their observed ranges due to the broken L µ − L τ symmetry. The second complex scalar is shown to be stable and becomes the dark matter candidate in our model. We show that while the Z µτ portal is ineffective for the parameters needed to explain the anomalous muon (g − 2) data, the correct dark matter relic abundance can easily be obtained from annihilation through the Higgs portal. Annihilation of the scalar dark matter in our model can also explain the Galactic Centre gamma ray excess observed by Fermi-LAT. We show the predictions of our model for future direct detection experiments and neutrino oscillation experiments.

A call for new physics: The muon anomalous magnetic moment and lepton flavor violation

“…It has been noted, however, that gauging any difference between two lepton family numbers with an Abelian group leads to an anomaly free theory [468,469,469,470]. L µ − L τ is an explicit example which has been investigated in detail in [471][472][473][474][475][476][477][478][479][480][481]. The gauge group …”

FIMP and muon (g − 2) in a U(1) Lμ−Lτ model

“…In our earlier work in ref. [32], we showed that our model can explain the nonzero neutrino masses and their intergenerational mixing angles. Also in that work, we considered the scalar field φ DM as a WIMP type dark matter candidate and checked its viability in various direct detection experiments.…”

“…The difference here with the previous work is that here we wish to produced the dark matter via the freeze-in mechanism instead of freeze-out, as in [32]. Our aim is to simultaneously explain the dark matter relic abundance as well as the muon (g − 2).…”

“…There are many well motivated extensions of the SM like SUSY, two Higgs doublet model, extension of the SM gauge group by extra U(1) and many more. In this work we have extended the SM gauge group by a local U(1) Lµ−Lτ symmetry [31][32][33]. Therefore, the complete gauge group in this model is SU(2) L × U(1) Y × U(1) Lµ−Lτ .…”

“…In our previous work [32] we studied in detail the muon (g − 2) and neutrino mass phenomenology in the framework of present model. The difference here with the previous work is that here we wish to produced the dark matter via the freeze-in mechanism instead of freeze-out, as in [32].…”