Electromagnetic Leptogenesis -- an EFT-Consistent Analysis via Wilson Coefficients I: Low-Scale, Non-Resonant Regime

We analyse electromagnetic leptogenesis within the framework of an effective field theory, where the dynamics is governed by the gauge-invariant dipole operator ONB. The Wilson coefficient CNB is matched at one loop and renormalisation-group (RG) evolved to the electroweak scale. After electroweak symmetry breaking we compute flavour-dependent two-body decay widths and CP asymmetries for N→ν+γ/Z, and solve the fully flavoured Boltzmann equations. In the N₁-dominated regime the freeze-out baryon asymmetry is YBFO 10⁻¹⁷, far below the observed value YBᵒᵇˢ 8.7× 10⁻¹¹. The suppression is structural: gauge invariance forces a Higgs insertion; therefore dipole couplings μ∝ v/M_Ψ² while the matched coefficient CNB is loop-generated and further reduced by RG running. We note that in the quasi-degenerate limit the self-energy resonance can be operative and suggest a plausible path to YBᵒᵇˢ.