Systematic study of the d = 5 Weinberg operator at one-loop order

By F. Bonnet, M. Hirsch, T. Ota, Walter Winter. 2012

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A bstractWe perform a systematic study of the d = 5 Weinberg operator at the one-loop level. We identify three different categories of neutrino mass generation: (1) finite irreducible diagrams; (2) finite extensions of the usual seesaw mechanisms at one-loop and (3) divergent loop realizations of the seesaws. All radiative one-loop neutrino mass models must fall into one of these classes. Case (1) gives the leading contribution to neutrino mass naturally and a classic example of this class is the Zee model. We demonstrate that in order to prevent that a tree level contribution dominates in case (2), Majorana fermions running in the loop and an additional $ {\mathbb{Z}_2} $ symmetry are needed for a genuinely leading one-loop contribution. In the type-II loop extensions, the Yukawa coupling will be generated at one loop, whereas the type-I/III extensions can be interpreted as loop-induced inverse or linear seesaw mechanisms. For the divergent diagrams in category (3), the tree level contribution cannot be avoided and is in fact needed as counter term to absorb the divergence.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/932d36ea938a83daf7d76e65a67a399bceb54212

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In Nuclear and High Energy Physics

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From the Trees to the Forest: A Review of Radiative Neutrino Mass Models (2017, background): “vely. Based on our knowledge, there are currently no models based on topologies T4-2-i and T4-3-i in the literature. Finally, although the topology T4-2-ii shown in Fig. 6c has been discarded in Ref. [100], because it is generally accompanied by the tree-level type-II seesaw mechanism, there are thr”