3 research outputs found
A Model of Quark and Lepton Masses I: The Neutrino Sector
If neutrinos have masses, why are they so tiny? Are these masses of the Dirac
type or of the Majorana type? We are already familiar with the mechanism of how
to obtain a tiny Majorana neutrino mass by the famous see-saw mechanism. The
question is: Can one build a model in which a tiny Dirac neutrino mass arises
in a more or less "natural" way? What would be the phenomenological
consequences of such a scenario, other than just merely reproducing the
neutrino mass patterns for the oscillation data? In this article, a systematic
and detailed analysis of a model is presented, with, as key components, the
introduction of a family symmetry as well as a new SU(2) symmetry for the
right-handed neutrinos. In particular, in addition to the calculations of light
neutrino Dirac masses, interesting phenomenological implications of the model
will be presented.Comment: 25 (single-spaced) pages, 11 figures, corrected some typos in Table
I, added acknowledgement
On Neutrino Masses and Family Replication
The old issue of why there are more than one family of quarks and leptons is
reinvestigated with an eye towards the use of anomaly as a tool for
constraining the number of families. It is found that, by assuming the
existence of right-handed neutrinos (which would imply that neutrinos will have
a mass) and a new chiral SU(2) gauge theory, strong constraints on the number
of families can be obtained. In addition, a model, based on that extra SU(2),
is constructed where it is natural to have one "very heavy" fourth neutrino and
three almost degenerate light neutrinos whose masses are all of the Dirac type.Comment: RevTex, 12 pages with 1 figure, minor changes to the text and added
acknowledgment
Quarks and Leptons Beyond the Third Generation
The possibility of additional quarks and leptons beyond the three generations
already established is discussed. The make-up of this Report is (I)
Introduction: the motivations for believing that the present litany of
elementary fermions is not complete; (II) Quantum Numbers: possible assignments
for additional fermions; (III) Masses and Mixing Angles: mass limits from
precision electroweak data, vacuum stability and perturbative gauge
unification; empirical constraints on mixing angles; (IV) Lifetimes and Decay
Modes: their dependence on the mass spectrum and mixing angles of the
additional quarks and leptons; the possibility of exceptionally long lifetimes;
(V) Dynamical Symmetry Breaking: the significance of the top quark and other
heavy fermions for alternatives to the elementary Higgs Boson; (VI) CP
Violation: extensions to more generations and how strong CP may be solved by
additional quarks; (VII) Experimental Searches: present status and future
prospects; (VIII) Conclusions.Comment: 139 pages, 27 figures, 267 references, version to appear in Physics
Report