Electromagnetic Leptogenesis -- an EFT-Consistent Analysis via Wilson Coefficients. Part II. Low-Scale, Resonant Regime

Abstract

We study electromagnetic leptogenesis (EMLG) in the low-scale, resonant regime within a fully effective-field-theory (EFT)--consistent framework. Starting from a UV Lagrangian and performing a one-loop matching to obtain the gauge-invariant dipole operator $O_{NB}$ with its Wilson coefficient $C_{NB}$, we implement the Pilaftsis--Underwood resummation for the self-energy contributions to the CP asymmetries and evolve a flavour covariant transport system across the electroweak window. In the quasi-degenerate limit $M_m-M_i\simeq\varGamma_m/2$, the CP-odd source acquires a Breit--Wigner--form enhancement whereas the washout saturates, with the freeze-out baryon asymmetry achieving $Y_B^{\rm FO}\gtrsim 10^{-10}$ across the strong-washout regime, comfortably above the observed value $Y_B^{\rm obs}\simeq 8.7\times 10^{-11}$. This establishes resonant EMLG at $O(100)~{\rm GeV}$ as a viable EFT-based mechanism for the baryon asymmetry of the Universe.