Article

# Neutrino Masses and A TeV Scale Seesaw Mechanism

Physical review D: Particles and fields 03/2010; DOI: 10.1103/PhysRevD.82.016008

Source: arXiv

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**ABSTRACT:**We use the discrete group \Sigma(81) = (Z_3 x Z_3 x Z_3)\rx Z_3 to suggest a relation among the off-diagonal entries of the neutrino mass matrix, as well as to explain the muon magnetic moment anomaly, a_\mu^exp-a_\mu^SM ~ 10^{-9}. We predict three new nearly degenerate Higgs doublets with masses of order ~500 GeV to ~ 1 TeV, and three nearly degenerate SM-singlet TeV-scale neutrinos. The largest scale in the model is ~10 TeV, so there is no severe hierarchy problem. The appendix is devoted to the group theory of \Sigma(81).Nuclear Physics B 02/2012; 871(3). · 4.33 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**Neutrinoless double beta ($0\nu\beta\beta$) decay can in general produce electrons of either chirality, in contrast with the minimal Standard Model (SM) extension with only the addition of the Weinberg operator, which predicts two left-handed electrons in the final state. We classify the lepton number violating (LNV) effective operators with two leptons of either chirality but no quarks, ordered according to the magnitude of their contribution to \znbb decay. We point out that, for each of the three chirality assignments, $e_Le_L, e_Le_R$ and $e_Re_R$, there is only one LNV operator of the corresponding type to lowest order, and these have dimensions 5, 7 and 9, respectively. Neutrino masses are always induced by these extra operators but can be delayed to one or two loops, depending on the number of RH leptons entering in the operator. Then, the comparison of the $0\nu\beta\beta$ decay rate and neutrino masses should indicate the effective scenario at work, which confronted with the LHC searches should also eventually decide on the specific model elected by nature. We also list the SM additions generating these operators upon integration of the heavy modes, and discuss simple realistic examples of renormalizable theories for each case.Journal of High Energy Physics 04/2012; 2012(6). · 5.62 Impact Factor -
##### Article: Hidden from View: Neutrino Masses, Dark Matter and TeV-Scale Leptogenesis in a Neutrinophilic 2HDM

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**ABSTRACT:**We consider a simple extension of the Standard Model providing dark matter and a TeV-scale seesaw mechanism that also allows for viable leptogenesis. In addition to the Standard Model degrees of freedom, the model contains a neutrinophilic Higgs doublet, a scalar singlet, and six singlet fermions (including three right-handed Majorana neutrinos) that are charged under a local $U(1)^\prime$ gauge symmetry. We show how the $U(1)^\prime$ charge assignments and the choice of scalar potential can lead to a TeV-scale seesaw mechanism and $\mathcal{O}(1)$ neutrino Yukawa couplings in a straightforward way. While this scenario has all the ingredients one would expect for significant experimental signatures, including several new TeV scale degrees of freedom, we find that most distinctive features associated with neutrino mass generation, leptogenesis and the dark sector are likely to remain inaccessible in the absence of additional lepton flavor symmetries.12/2012;

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