Charged lepton flavor violating radiative decays li→ ljγ in G2HDM

We compute the electromagnetic form factors of the l(i)l(j)gamma vertex at one-loop level in the minimal G2HDM which has a sub-GeV vector dark matter candidate. The results are applied to the radiative decay rates for the charged lepton flavor violating processes l(i) -> l(j)gamma, and the anomalous magnetic dipole moment and the electric dipole moment of the charged lepton. To numerically compute the branching ratio for mu -> e gamma and compare with the latest experimental limit from MEG, we adapt our previous parameter space scan that is consistent with the relic density and constraints from direct searches of dark matter, W and Z mass measurements, as well as the LHC Higgs signal strengths and invisible width. While the extra contributions are at least an order of magnitude smaller than required to explain the similar to 4.2 sigma discrepancy in the muon anomaly, the existing MEG limit imposes stringent constraint on the parameter space. The remaining viable parameter space can be further probed by the MEG II sensitivity for mu -> e gamma as well as from the direct searches of sub-GeV dark matter in foreseeable future. Higher loop contributions may be significant to resolve the discrepancy in the muon anomaly and generate a non-vanishing electric dipole moments for the standard model quarks and leptons in G2HDM.

Automated summary

We calculate the electromagnetic form factors of the l(i)l(j)gamma vertex in the minimal G2HDM at one-loop level, incorporating a sub-GeV vector dark matter candidate. The results are used to study charged lepton flavor violating processes, as well as the magnetic and electric dipole moments of charged leptons. Our parameter space scan, satisfying relic density, direct dark matter searches, and other constraints, allows for the computation of the branching ratio for mu -> e gamma and comparison with the latest experimental limit from MEG. The MEG constraint imposes strong limitations on the viable parameter space, but future experiments and higher loop contributions may provide further insights.