Muon ($g-2$) in $U(1)_{L_{\mu}-L_{\tau}}$ Scotogenic Model Extended with Vector like Fermion

TL;DR

This paper explores an extended scotogenic model with a $U(1)_{L_{}-L_{ au}}$ symmetry and vector-like fermions to explain the muon ($g-2$) anomaly, neutrino masses, and related phenomenology, constrained by current experimental data.

Contribution

It introduces a vector-like lepton triplet extension to the gauged scotogenic model, providing a chirally enhanced contribution to muon ($g-2$) independent of $Z_{}$ mass, and analyzes its implications for neutrino physics and $0 uetaeta$ decay.

Findings

Identified two $Z_{}$ mass regions explaining muon ($g-2$) within neutrino data constraints.

Region I is consistent with muon neutrino trident bounds; Region II violates them for $M_{Z_{}}>300$ MeV.

The VLL extension offers a significant positive contribution to muon ($g-2$), compatible with experimental bounds.

Abstract

The latest results of anomalous muon magnetic moment at Fermilab show a discrepancy of 4.2 $\sigma$ between the Standard Model (SM) prediction and experimental value. In this work, we revisit $U(1)_{L_{\mu}-L_{\tau}}$ symmetry with in the paradigm of scotogenic model which explains muon ($g-2$) and neutrino mass generation, simultaneously. The mass of new gauge boson $M_{Z_{\mu\tau}}$ generated after the spontaneous symmetry breaking of $U(1)_{L_{\mu}-L_{\tau}}$ is constrained, solely, in light of the current neutrino oscillation data to explain muon ($g-2$). In particular, we have obtained two regions I and II, around 150 MeV and 500 MeV, respectively, in $M_{Z_{\mu\tau}}-g_{\mu\tau}$ plane which explain the neutrino phenomenology. Region I is found to be consistent with muon neutrino trident (MNT) bound ($g_{\mu\tau}$ $\leq$ $10^{-3}$) to explain muon ($g-2$), however, region II violates it for mass range $M_{Z_{\mu\tau}}>300$ MeV. We, then, extend the minimal gauged scotogenic model by a vector like lepton (VLL) triplet $\psi_T$. The mixing of $\psi_T$ with inert scalar doublet $\eta$ leads to chirally enhanced positive contribution to muon anomalous magnetic moment independent of $Z_{\mu\tau}$ mass. Furthermore, we have, also, investigated the implication of the model for $0\nu\beta\beta$ decay and $CP$ violation. The non-observation of $0\nu\beta\beta$ decay down to the sensitivity of 0.01 eV shall refute the model. The model, in general,is found to be consistent with both $CP$ conserving and $CP$ violating solutions.