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

Citation
J. Ellis et al., Neutrino textures in light of Super-Kamiokande data and a realistic stringmodel, EUR PHY J C, 9(3), 1999, pp. 389-408
Citations number
84
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physics
Journal title
EUROPEAN PHYSICAL JOURNAL C
ISSN journal
1434-6044 → ACNP
Volume
9
Issue
3
Year of publication
1999
Pages
389 - 408
Database
ISI
SICI code
1434-6044(199907)9:3<389:NTILOS>2.0.ZU;2-U
Abstract
Motivated by the Super-Kamiokande atmospheric neutrino data, we discuss pos sible textures for Majorana and Dirac neutrino masses within the see-saw fr amework. There are two main purposes of this paper: first, to gain intuitio n into this area from a purely phenomenological analysis, and second, to ex plore to what extent it may be realized in a specific model. We comment ini tially on the simplified two-generation case, emphasizing that large mixing is not incompatible with a large hierarchy of mass eigenvalues. We also em phasize that renormalization-group effects may amplify neutrino mixing, and we present semi-analytic expressions for estimating this amplification. Se veral 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 feat ures of neutrino mass textures arising in models with a U(1) flavour symmet ry. Finally, we discuss the possible pattern of neutrino masses in a "reali stic" flipped SU(5) model derived from string theory, illustrating how a de sirable pattern of mixing may emerge. Both small- or large-angle MSW soluti ons 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 state s may include extra gauge-singlet fields.