Lepton Flavor Physics in the flipped 3-3-1-1 Model: Non-Universality and Violation

TL;DR

The paper investigates lepton flavor violation and lepton non-universality in the flipped 3-3-1-1 (F3311) model, focusing on Z-boson decays, l_i→l_jγ, and leptonic three-body decays to constrain the Z–Z' mixing and heavy gauge masses. It develops the neutral-current structure, derives one-loop contributions to charged-current transitions, and performs a comprehensive numerical analysis linking exotic masses and dark matter candidates to experimental observables, including R(D) and R(D*). The study finds that the model can address the observed anomalies in B decays while respecting stringent LFV bounds, with a viable DM candidate in the TeV range and heavy exotic fermions and quarks at multi-TeV scales. Overall, F3311 offers a coherent framework that ties LFV, LFU violation, DM stability via a residual symmetry, and flavor anomalies into a testable set of predictions for current and upcoming experiments.

Abstract

We investigate the flavor violation (FV) of Z decays to leptons at tree level and flavor conserving Z decays to leptons in the frame work of the flipped $ SU(3)_C\otimes SU(3)_L \otimes U(1)_X\otimes U(1)_N$,(F3311) model. In addition, we analyze the processes $l_i\rightarrow l_j γ$ and the leptonic three-body decay. Using the experimental bounds on these decays we set the constraint on $\sin φ$ which represents the mixing between Z-Z' boson. The most stringent limits arises from $μ\rightarrow e γ$ decay where $\sin φ\sim \mathcal{ O}(10^{-3})$. The leptonic three-body decay set lower bound on the mass of the new neural gauge boson $m_{Z'} \geq 3.2TeV$. Using the LUX-ZEPLIN (LZ) experiment data we set bounds to the mass of the dark matter candidates. Subsequently, we investigate the lepton non-universality in B decays within the $F3311$ model by calculating the generic one-loop contribution to the process $u_i\rightarrow d_j e_b \barν_a$ in the unitary gauge as well as numerical evaluating the branching ratio $R_D, R_{D^{(*)}},R(X_c)$. We demonstrate that the $F3311$ model can address the $3.3 σ$ discrepancies between Standard Model and experimental data. To reaffirm our results, we also analyze the $d \to u$ transitions and $s\to u$ transitions. These two transitions also give consistent result with experiment data. Combine all experiment dat a we obtain the operating region for the mass of the model specifically $m_E \in [6.5, 9 ]TeV$, $m_Q \in [6,11]TeV$ and the dark matter candidate $m_ξ\in [1.5,2 ]TeV$.

Figures (16)

• Figure 1: Allowed region of $Br(Z\rightarrow l_i l_j)$. Blue region is the combined region restricted by experimental values.
• Figure 2: 1-loop contribution to $Z_1\rightarrow l_i l_i$ decay.
• Figure 3: Condition for $90\% C.L$ for $Br(Z\rightarrow e^+e^-)$
• Figure 4: Loop diagrams for process $l_i \rightarrow l_j \gamma$
• Figure 5: Allowed region of parameter space ($m_{Z_2}, s_{\phi}$) of $\mu \rightarrow e \gamma$