2018 Impact factor 4.843
Particles and Fields
Eur. Phys. J. C 9, 389-408
DOI 10.1007/s100529900001

Neutrino textures in light of Super-Kamiokande data and a realistic string model

J. Ellis1 - G.K. Leontaris1,2 - S. Lola1 - D.V. Nanopoulos3,4,5

1 Theory Division, CERN, CH-1211 Geneva 23, Switzerland
2 Theoretical Physics Division, Ioannina University, GR-45110 Ioannina, Greece
3 Center for Theoretical Physics, Department of Physics, Texas A&M University, College Station, TX 77843 4242, USA
4 Astroparticle Physics Group, Houston Advanced Research Center (HARC), The Mitchell Campus, Woodlands, TX 77381, USA
5 Academy of Athens, Chair of Theoretical Physics, Division of Natural Sciences, 28 Panepistimiou Ave., Athens GR-10679, Greece

Received: 6 November 1998 / Published online: 18 June 1999

Abstract
Motivated by the Super-Kamiokande atmospheric neutrino data, we discuss possible textures for Majorana and Dirac neutrino masses within the see-saw framework. There are two main purposes of this paper: first, to gain intuition into this area from a purely phenomenological analysis, and second, to explore to what extent it may be realized in a specific model. We comment initially on the simplified two-generation case, emphasizing that large mixing is not incompatible with a large hierarchy of mass eigenvalues. We also emphasize that renormalization-group effects may amplify neutrino mixing, and we present semi-analytic expressions for estimating this amplification. Several examples are then given of three-family neutrino mass textures, which may also accommodate the persistent solar neutrino deficit, with different assumptions for the neutrino Dirac mass matrices. We comment on a few features of neutrino mass textures arising in models with a U(1) flavour symmetry. Finally, we discuss the possible pattern of neutrino masses in a "realistic'' flipped SU(5) model derived from string theory, illustrating how a desirable pattern of mixing may emerge. Both small- or large-angle MSW solutions are possible, while a hierarchy of neutrino masses appears more natural than near-degeneracy. This model contains some unanticipated features that may be relevant in other models also: The neutrino Dirac matrices may not be related closely to the quark mass matrices, and the heavy Majorana states may include extra gauge-singlet fields.


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