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 ${\kappa }_{\mathrm{match}}=3\mathrm{TeV}$, a factorized flavor structure, and ${\tilde{m}}_1^{\mathrm{EM}}=3.97\times 10^{-2}\mathrm{eV}$. Since these inputs do not determine $Y_{\nu }$, we impose the conditional width bound ${\Gamma }_Y^{(0)}⩽ϵ{\Gamma }_{\mathrm{EM}}^{(0)}$ 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 $ϵ=10^{-2}$ and two coherently aligned heavy states, the width-only envelopes are $\mathrm{BR}(\mu \to e\gamma )⩽2.77\times 10^{-28}$, $|d_e|⩽5.71\times 10^{-37}e\mathrm{cm}$, and $|\Delta a_{\mu }|⩽1.31\times 10^{-21}$. The factorized flavor structure and $C_{NW}/C_{NB}=1.739$ give smaller conditional bounds. The benchmark phase ${\varphi }_{BW}=0$, 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 $\Delta M/M_1$.

Comments: 10 pages, 3 figures