<p>We analyse electromagnetic leptogenesis within the framework of an effective field theory, where the dynamics is governed by the gauge-invariant dipole operator <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\({\mathcal{O}}_{NB}=\left(\overline{L}{\sigma }^{\mu \nu }N\right)\widetilde{H}{B}_{\mu \nu }\)</EquationSource> </InlineEquation>. The Wilson coefficient <i>C</i><sub><i>NB</i></sub> 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 <i>N</i> → <i>νγ</i> and <i>N</i> → <i>νZ</i>, and solve the fully flavoured Boltzmann equations. In the <i>N</i><sub>1</sub>-dominated regime, the freeze-out baryon asymmetry is <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\({Y}_{B}^{\text{FO}}\lesssim {1}{0}^{-{17}}\)</EquationSource> </InlineEquation>, far below the observed value <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\({Y}_{B}^{\text{obs}}\simeq 8.7\times {10}^{-11}\)</EquationSource> </InlineEquation>. The suppression is structural: gauge invariance forces a Higgs insertion; therefore the dipole coupling scales as <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\mu \propto v/{M}_{\psi}^{2}\)</EquationSource> </InlineEquation>, while the matched Wilson coefficient <i>C</i><sub>NB</sub> 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 <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\({Y}_{B}^{\text{obs}}\)</EquationSource> </InlineEquation>.</p>

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Electromagnetic leptogenesis — an EFT-consistent analysis via Wilson coefficients. Part I. Low-scale, non-resonant regime

  • Rin Takada

摘要

We analyse electromagnetic leptogenesis within the framework of an effective field theory, where the dynamics is governed by the gauge-invariant dipole operator \({\mathcal{O}}_{NB}=\left(\overline{L}{\sigma }^{\mu \nu }N\right)\widetilde{H}{B}_{\mu \nu }\) . The Wilson coefficient CNB 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 Nνγ and NνZ, and solve the fully flavoured Boltzmann equations. In the N1-dominated regime, the freeze-out baryon asymmetry is \({Y}_{B}^{\text{FO}}\lesssim {1}{0}^{-{17}}\) , far below the observed value \({Y}_{B}^{\text{obs}}\simeq 8.7\times {10}^{-11}\) . The suppression is structural: gauge invariance forces a Higgs insertion; therefore the dipole coupling scales as \(\mu \propto v/{M}_{\psi}^{2}\) , while the matched Wilson coefficient CNB 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 \({Y}_{B}^{\text{obs}}\) .