Radiative neutrino mass model from a mass dimension-11 \u2206L = 2 effective operator

Abstract

We present the first detailed phenomenological analysis of a radiative Majorana neutrino mass model constructed from opening up a ∆L = 2 mass-dimension-11 effective operator constructed out of standard model fields. While three such operators are generated, only one dominates neutrino mass generation, namely {O}_{47}=overline{L^C}Loverline{Q^C}Loverline{Q}{Q}^C HH, where L denotes lepton doublet, Q quark doublet and H Higgs doublet. The under- lying renormalisable theory contains the scalars {S}_1sim left(overline{3},1,1/3right) coupling as a diquark, {S}_3sim left(overline{3},3,1/3right) coupling as a leptoquark, and Φ3 ∼ (3, 3, 2/3), which has no Yukawa couplings but does couple to S1 and S3 in addition to the gauge fields. Neutrino masses and mixings are generated at two-loop order. A feature of this model that is different from many other radiative models is the lack of proportionality to any quark and charged- lepton masses of the neutrino mass matrix. One consequence is that the scale of new physics can be as high as 107 TeV, despite the operator having a high mass dimension. This raises the prospect that ∆L = 2 effective operators at even higher mass dimensions may, when opened up, produce phenomenologically-viable radiative neutrino mass models. The parameter space of the model is explored through benchmark slices that are subject to experimental constraints from charged lepton flavour-violating decays, rare meson de- cays and neutral-meson mixing. The acceptable parameter space can accommodate the anomalies in RK (∗) and the anomalous magnetic moment of the muon.