Electromagnetic leptogenesis — an EFT-consistent analysis via Wilson coefficients. Part 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=(L̄σ μ νN)HBμ ν . The Wilson coefficient C NB is matched at one loop and evolved to the electroweak scale via renormalisation-group (RG) running. After electroweak symmetry breaking, we compute flavour-dependent decay widths and CP asymmetries for the two-body modes N → νγ and N → νZ , and solve the fully flavoured Boltzmann equations. In the N 1 -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 the dipole coupling scales as μ ∝ v/Mψ² , while the matched Wilson coefficient C NB is loop-generated and further suppressed 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 .