arXiv subjects

Stéphane Lavignac

Publications and source records attributed to Stéphane Lavignac.

21 records · Page 2Linked to original sources

arXiv1997

A Guide to Flat Direction Analysis in Anomalous U(1) Models

We suggest a systematic procedure to study D- and F-flat directions in a large class of models with an anomalous U(1). This class of models is characterized by the existence of a vacuum that breaks all Abelian gauge symmetries connecting the observable sector to the hidden sector. We show that, under some conditions, there is no other stable vacuum that breaks these symmetries. As a consequence, the model yields definite (order of magnitude) predictions for low-energy mass hierarchies. Then we study generic flat directions and identify the ones that may lead to undesirable vacua. We give necessary conditions for those to be lifted, and show that supersymmetry breaking only slightly affects the conclusions from the flat direction analysis.

hep-ph↗

arXiv1996

Neutrino Mass Models with an Abelian Family Symmetry

Abelian family symmetries provide a predictive framework for neutrino mass models. In seesaw models based on an abelian family symmetry, the structures of the Dirac and the Majorana matrices are derived from the symmetry, and the neutrino masses and mixing angles are determined by the lepton charges under the family symmetry. Such models can lead to mass degeneracies and large mixing angles as well as mass hierarchies, the squared mass difference between quasi-degenerate neutrinos being determined by the symmetry. We present two models illustrating this approach.

hep-ph↗

arXiv1996

Neutrino Masses and Family Symmetries

The hypothesis of an additional abelian symmetry acting in a different way on the three families of leptons leads to interesting predictions in the neutrino sector. Contrary to what happens in most seesaw models, the structures of the Dirac and the Majorana matrices are determined without any ansatz, and the neutrino masses and mixing angles are fixed once the lepton charges under the family symmetry have been chosen. Two explicit models using this idea are presented.

hep-ph↗