Neutrino textures in light of SuperKamiokande data and a realistic string model
Abstract
Motivated by the SuperKamiokande atmospheric neutrino data, we discuss possible textures for Majorana and Dirac neutrino masses within the seesaw 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 twogeneration case, emphasizing that large mixing is not incompatible with a large hierarchy of mass eigenvalues. We also emphasize that renormalizationgroup effects may amplify neutrino mixing, and we present semianalytic expressions for estimating this amplification. Several examples are then given of threefamily 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 largeangle MSW solutions are possible, while a hierarchy of neutrino masses appears more natural than neardegeneracy. 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 gaugesinglet fields.
 Publication:

European Physical Journal C
 Pub Date:
 1999
 arXiv:
 arXiv:hepph/9808251
 Bibcode:
 1999EPJC....9..389E
 Keywords:

 High Energy Physics  Phenomenology
 EPrint:
 LaTex 37 pages, with 5 eps figures