1,252 research outputs found
Seesaw mechanism in three flavors
We advance a method used to analyse the neutrino properties (masses and
mixing) in the seesaw mechanism. Assuming the hierarchical Dirac and light
neutrino masses we establish rather simple relations between the light and the
heavy neutrino parameters in the favored region of the solar and the
atmospheric neutrino experiments. A empirical condition satisfied by the RH
mixing angles is obtained.Comment: 19 pages. Acceptted by Phys. Rev. D The part about the neutrino
experiments is selected as a single section. The mistakes in spelling and
grammer are corrected. Also, some equations are neewly numbere
Mass Hierarchies and the Seesaw Neutrino Mixing
We give a general analysis of neutrino mixing in the seesaw mechanism with
three flavors. Assuming that the Dirac and u-quark mass matrices are similar,
we establish simple relations between the neutrino parameters and individual
Majorana masses. They are shown to depend rather strongly on the physical
neutrino mixing angles. We calculate explicitly the implied Majorana mass
hierarchies for parameter sets corresponding to different solutions to the
solar neutrino problem.Comment: 11 pages, no figures, replaced with final version. Minor corrections
and one typo corrected. Added one referenc
Continuity of Local Time: An applied perspective
Continuity of local time for Brownian motion ranks among the most notable
mathematical results in the theory of stochastic processes. This article
addresses its implications from the point of view of applications. In
particular an extension of previous results on an explicit role of continuity
of (natural) local time is obtained for applications to recent classes of
problems in physics, biology and finance involving discontinuities in a
dispersion coefficient. The main theorem and its corollary provide physical
principles that relate macro scale continuity of deterministic quantities to
micro scale continuity of the (stochastic) local time.Comment: To appear in: "The fascination of Probability, Statistics and Their
Applications. In honour of Ole E. Barndorff-Nielsen on his 80th birthday
Three-generation study of neutrino spin-flavor conversion in supernova and implication for neutrino magnetic moment
We investigate resonant spin-flavor (RSF) conversions of supernova neutrinos
which are induced by the interaction of neutrino magnetic moment and supernova
magnetic fields. From the formulation which includes all three-flavor neutrinos
and anti-neutrinos, we give a new crossing diagram that includes not only
ordinary MSW resonance but also magnetically-induced RSF effect. With the
diagram, it is found that four conversions occur in supernova, two are induced
by the RSF effect and two by the pure MSW. We also numerically calculate
neutrino conversions in supernova matter, using neutrino mixing parameters
inferred from recent experimental results and a realistic supernova progenitor
model. The results indicate that until 0.5 seconds after core bounce, the
RSF-induced transition occurs
efficiently (adiabatic resonance), when \mu_\nu \agt 10^{-12} \mu_B
(B_0 / 5 \times 10^{9} \mathrm G)^{-1}, where is the strength of the
magnetic field at the surface of iron core. We also evaluate the energy
spectrum as a function of at the SuperKamiokande detector and the
Sudbury Neutrino Observatory using the calculated conversion probabilities, and
find that the spectral deformation might have possibility to provide useful
information on neutrino magnetic moment as well as magnetic field strength in
supernovae.Comment: 35 pages, 13 figure
Identifying the neutrino mass spectrum from a supernova neutrino burst
We study the role that the future detection of the neutrino burst from a
galactic supernova can play in the reconstruction of the neutrino mass
spectrum. We consider all possible 3 mass and flavor spectra which
describe the solar and atmospheric neutrino data. For each of these spectra we
find the observable effects of the supernova neutrino conversions both in the
matter of the star and the earth. We show that studies of the electron neutrino
and anineutrino spectra as well as observations of the neutral current effects
from supernova will allow us (i) to identify the solar neutrino solution, (ii)
to determine the type of mass hierarchy (normal or inverted) and (iii) to probe
the mixing to values as low as .Comment: 53 pages, 13eps figures. Substantial changes made, new results,
figures and tables adde
Urban community gardeners' knowledge and perceptions of soil contaminant risks
Although urban community gardening can offer health, social, environmental, and economic benefits, these benefits must be weighed against the potential health risks stemming from exposure to contaminants such as heavy metals and organic chemicals that may be present in urban soils. Individuals who garden at or eat food grown in contaminated urban garden sites may be at risk of exposure to such contaminants. Gardeners may be unaware of these risks and how to manage them. We used a mixed quantitative/qualitative research approach to characterize urban community gardeners' knowledge and perceptions of risks related to soil contaminant exposure. We conducted surveys with 70 gardeners from 15 community gardens in Baltimore, Maryland, and semi-structured interviews with 18 key informants knowledgeable about community gardening and soil contamination in Baltimore. We identified a range of factors, challenges, and needs related to Baltimore community gardeners' perceptions of risk related to soil contamination, including low levels of concern and inconsistent levels of knowledge about heavy metal and organic chemical contaminants, barriers to investigating a garden site's history and conducting soil tests, limited knowledge of best practices for reducing exposure, and a need for clear and concise information on how best to prevent and manage soil contamination. Key informants discussed various strategies for developing and disseminating educational materials to gardeners. For some challenges, such as barriers to conducting site history and soil tests, some informants recommended city-wide interventions that bypass the need for gardener knowledge altogether
A bovine lymphosarcoma cell line infected with theileria annulata exhibits an irreversible reconfiguration of host cell gene expression
Theileria annulata, an intracellular parasite of bovine lymphoid cells, induces substantial phenotypic alterations to its host cell including continuous proliferation, cytoskeletal changes and resistance to apoptosis. While parasite induced modulation of host cell signal transduction pathways and NFκB activation are established, there remains considerable speculation on the complexities of the parasite directed control mechanisms that govern these radical changes to the host cell. Our objectives in this study were to provide a comprehensive analysis of the global changes to host cell gene expression with emphasis on those that result from direct intervention by the parasite. By using comparative microarray analysis of an uninfected bovine cell line and its Theileria infected counterpart, in conjunction with use of the specific parasitacidal agent, buparvaquone, we have identified a large number of host cell gene expression changes that result from parasite infection. Our results indicate that the viable parasite can irreversibly modify the transformed phenotype of a bovine cell line. Fifty percent of genes with altered expression failed to show a reversible response to parasite death, a possible contributing factor to initiation of host cell apoptosis. The genes that did show an early predicted response to loss of parasite viability highlighted a sub-group of genes that are likely to be under direct control by parasite infection. Network and pathway analysis demonstrated that this sub-group is significantly enriched for genes involved in regulation of chromatin modification and gene expression. The results provide evidence that the Theileria parasite has the regulatory capacity to generate widespread change to host cell gene expression in a complex and largely irreversible manner
Is Large Lepton Mixing Excluded?
The original \bnum -(or -) energy spectrum from the
gravitational collapse of a star has a larger average energy than the spectrum
for \bnue since the opacity of \bnue exeeds that of \bnum (or ).
Flavor neutrino conversion, \bnue \bnum, induced by lepton
mixing results in partial permutation of the original \bnue and \bnum spectra.
An upper bound on the permutation factor, (99 CL) is derived
using the data from SN1987A and the different models of the neutrino burst. The
relation between the permutation factor and the vacuum mixing angle is
established, which leads to the upper bound on this angle. The excluded region,
, covers the regions of large mixing angle
solutions of the solar neutrino problem: ``just-so" and, partly, MSW, as well
as part of region of oscillation space which could be
responsible for the atmospheric muon neutrino deficit. These limits are
sensitive to the predicted neutrino spectrum and can be strengthened as
supernova models improve.Comment: 20 pages, TeX file. For hardcopy with figures contact
[email protected]. Institute for Advanced Study number AST 93/1
Three-flavor MSW solutions of the solar neutrino problem
We perform an updated phenomenological analysis of the
Mikheyev-Smirnov-Wolfenstein (MSW) solutions of the solar neutrino problem,
assuming oscillations between two and three neutrino families. The analysis
includes the total rates of the Homestake, SAGE, GALLEX, Kamiokande and
Super-Kamiokande experiments, as well as the day-night asymmetry and the 18-bin
energy spectrum of Super-Kamiokande. Solutions are found at several values of
the theta_{13} mixing angle. Among the most interesting features, we find that
solar neutrino data alone put the constraint theta_{13} < 55--59 deg at 95%
C.L., and that a fraction of the MSW solutions extends at and beyond maximal
(nu_1,nu_2) mixing (theta_{12} > pi/4), especially if the neutrino square mass
splitting is in its lower range (m^2_2-m^2_1 ~ 10^{-7} eV^2) and if theta_{13}
is nonzero. In particular, bimaximal (or nearly bimaximal) mixing is possible
for atmospheric and MSW solar neutrino oscillations within the stringent
reactor bounds on theta_{13}.Comment: 19 pages (RevTeX) + 14 figures (PostScript
Neutral Particles in Light of the Majorana-Ahluwalia Ideas
The first part of this article (Sections I and II) presents oneself an
overview of theory and phenomenology of truly neutral particles based on the
papers of Majorana, Racah, Furry, McLennan and Case. The recent development of
the construct, undertaken by Ahluwalia [{\it Mod. Phys. Lett. A}{\bf 9} (1994)
439; {\it Acta Phys. Polon. B}{\bf 25} (1994) 1267; Preprints LANL
LA-UR-94-1252, LA-UR-94-3118], could be relevant for explanation of the present
experimental situation in neutrino physics and astrophysics.
In Section III the new fundamental wave equations for self/anti-self
conjugate type-II spinors, proposed by Ahluwalia, are re-casted to covariant
form. The connection with the Foldy-Nigam-Bargmann-Wightman- Wigner (FNBWW)
type quantum field theory is found. The possible applications to the problem of
neutrino oscillations are discussed.Comment: REVTEX file. 21pp. No figure
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