205 research outputs found
Dark Matter in Nuclear Physics
This White Paper was prepared for the Nuclear Science Town Meeting on "Neutrinos, Neutrons and Fundamental Symmetries, held in Chicago on Jan. 17-19, 2007
Systematic Study of Fermion Masses and Mixing Angles in Horizontal SU(2) Gauge Theory
Despite its great success in explaining the basic interactions of nature, the
standard model suffers from an inability to explain the observed masses of the
fundamental particles and the weak mixing angles between them. We shall survey
a set of possible extensions to the standard model, employing an SU(2)
``horizontal'' gauge symmetry between the particle generations, to see what
light they can shed on this problem.Comment: 43 pages, 4 figures (available by postal mail on request), OZ-92/0
A Natural Framework for Solar and 17 keV Neutrinos
Motivated by recent experimental claims for the existence of a 17 keV
neutrino and by the solar neutrino problem, we construct a class of models
which contain in their low-energy spectrum a single light sterile neutrino and
one or more Nambu-Goldstone bosons. In these models the required pattern of
breaking of lepton-number symmetry takes place near the electroweak scale and
all mass heirarchies are technically natural. The models are compatible with
all cosmological and astrophysical constraints, and can solve the solar
neutrino problem via either the MSW effect or vacuum oscillations. The deficit
in atmospheric muon neutrinos seen in the Kamiokande and IMB detectors can also
be explained in these models.Comment: 23 page
Planck scale effects in neutrino physics
We study the phenomenology and cosmology of the Majoron (flavon) models of
three active and one inert neutrino paying special attention to the possible
(almost) conserved generalization of the Zeldovich-Konopinski-Mahmoud lepton
charge. Using Planck scale physics effects which provide the breaking of the
lepton charge, we show how in this picture one can incorporate the solutions to
some of the central issues in neutrino physics such as the solar and
atmospheric neutrino puzzles, dark matter and a 17 keV neutrino. These
gravitational effects induce tiny Majorana mass terms for neutrinos and
considerable masses for flavons. The cosmological demand for the sufficiently
fast decay of flavons implies a lower limit on the electron neutrino mass in
the range of 0.1-1 eV.Comment: 24 pages, 1 figure (not included but available upon request), LaTex,
IC/92/196, SISSA-140/92/EP, LMU-09/9
Pseudo-Dirac Scenario for Neutrino Oscillations
We argue how pseudo-Dirac scenario for neutrinos leads to rich neutrino
oscillation phenomena, including oscillation inside each generation. The
pseudo-Dirac scenario is generalized by incorporating generation mixings and
formulae for the various neutrino oscillations are derived. As the application
we compare the formulae with the corresponding data. We find that observed
pattern of mixings, such as almost maximal mixing in the atmospheric neutrino
oscillation, is naturally explained in the generalized Pseudo-Dirac scenario
with small generation mixings. We, however, also point out that there remain
some problems to be settled for this scenario to be viable. The possible
theoretical framework to realize the pseudo-Dirac scenario is also briefly
commented on.Comment: 17 pages, LaTeX fil
Planck-Scale Physics and Neutrino Masses
We discuss gravitationally induced masses and mass splittings of Majorana,
Zeldovich-Konopinski-Mahmoud and Dirac neutrinos. Among other implications,
these effects can provide a solution of the solar neutrino puzzle. In
particular, we show how this may work in the 17 keV neutrino picture.Comment: 10 pages, IC/92/79, SISSA-83/92/EP, LMU-04/92 (the preprint number
has been corrected; no other changes
A Monte Carlo simulation of the Sudbury Neutrino Observatory proportional counters
The third phase of the Sudbury Neutrino Observatory (SNO) experiment added an
array of 3He proportional counters to the detector. The purpose of this Neutral
Current Detection (NCD) array was to observe neutrons resulting from
neutral-current solar neutrino-deuteron interactions. We have developed a
detailed simulation of the current pulses from the NCD array proportional
counters, from the primary neutron capture on 3He through the NCD array
signal-processing electronics. This NCD array Monte Carlo simulation was used
to model the alpha-decay background in SNO's third-phase 8B solar-neutrino
measurement.Comment: 38 pages; submitted to the New Journal of Physic
A proposed measurement of the Ăź asymmetry in neutron decay with the Los Alamos Ultra-Cold Neutron Source
This article reviews the status of an experiment to study the neutron spin-electron angular correlation with the Los Alamos Ultra-Cold Neutron (UCN) source. The experiment will generate UCNs from a novel solid deuterium, spallation source, and polarize them in a solenoid magnetic field. The experiment spectrometer will consist of a neutron decay region in a solenoid magnetic field combined with several different detector possibilities. An electron beam and a magnetic spectrometer will provide a precise, absolute calibration for these detectors. An A-correlation measurement with a relative precision of 0.2% is expected by the end of 2002
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