Yukawa-assisted charged-lepton dipoles in resonant electromagnetic leptogenesis

Abstract

We study the charged-lepton dipole contribution that is linear in the neutrino-dipole coefficients $C_{NB,NW}$ and in the renormalizable neutrino Yukawa matrix $Y_\nu$. We consider a resonant EMLG benchmark with dipole-sector coefficients renormalized at $\kappa_N=M_1=1\,\mathrm{TeV}$ and evolved through the coupled one-loop RGE to $\kappa_{\rm match}=3\,\mathrm{TeV}$, a factorized flavor structure, and $\tilde{m}^{\rm EM}_1=3.97\times 10^{-2}\,\mathrm{eV}$. Since these inputs do not determine $Y_\nu$, we impose the conditional width bound $\Gamma_Y^{(0)}\leqslant\epsilon\Gamma_{\rm EM}^{(0)}$ and a vanishing direct ultraviolet charged-lepton dipole, derive the one-loop $\nu$SMEFT leading logarithm, and apply the tree-level electroweak projection and one-loop QED evolution in LEFT. For $\epsilon=10^{-2}$ and two coherently aligned heavy states, the width-only envelopes are $\mathrm{BR}(\mu\to e\gamma)\leqslant2.77\times10^{-28}$, $|d_e|\leqslant5.71\times10^{-37}\,e\,\mathrm{cm}$, and $|\Delta a_\mu|\leqslant1.31\times10^{-21}$. The factorized flavor structure and $C_{NW}/C_{NB}=1.739$ give smaller conditional bounds. The benchmark phase $\phi_{BW}=0$, for which $\rho_{BW}=+1.739$, lies near the charged-lepton photon-dipole blind direction. The vacuum local coefficient contains no resonant pole denominator. The two thermal pole prescriptions enter the low-energy comparison only through the mass splittings selected by the transport calculation, producing a relative change of order $\Delta M/M_1$.