4,958 research outputs found
KATRIN Sensitivity to Sterile Neutrino Mass in the Shadow of Lightest Neutrino Mass
The presence of light sterile neutrinos would strongly modify the energy
spectrum of the Tritium \beta-electrons. We perform an analysis of the KATRIN
experiment's sensitivity by scanning almost all the allowed region of neutrino
mass-squared difference and mixing angles of the 3+1 scenario. We consider the
effect of the unknown absolute mass scale of active neutrinos on the
sensitivity of KATRIN to the sterile neutrino mass. We show that after 3 years
of data-taking, the KATRIN experiment can be sensitive to mixing angles as
small as sin^2 (2\theta_s) ~ 10^-2. Particularly we show that for small mixing
angles, sin^2 (2\theta_s) < 0.1, the KATRIN experiment can gives the strongest
limit on active-sterile mass-squared difference.Comment: 4 pages, 2 figures, matches the published versio
Solar Model Parameters and Direct Measurements of Solar Neutrino Fluxes
We explore a novel possibility of determining the solar model parameters,
which serve as input in the calculations of the solar neutrino fluxes, by
exploiting the data from direct measurements of the fluxes. More specifically,
we use the rather precise value of the neutrino flux, obtained
from the global analysis of the solar neutrino and KamLAND data, to derive
constraints on each of the solar model parameters on which depends. We
also use more precise values of and fluxes as can be obtained from
future prospective data and discuss whether such measurements can help in
reducing the uncertainties of one or more input parameters of the Standard
Solar Model.Comment: 25 pages, 3 figure
Flavor Delta(54) in SU(5) SUSY Model
We design a supersymmetric SU (5) GUT model using \Delta (54), a finite
non-abelian subgroup of SU (3)f . Heavy right handed neutrinos are introduced
which transform as three-dimensional repre-sentation of our chosen family
group. The model successfully reproduces the mass hierarchical mass structures
of the Standard Model, and the CKM mixing matrix. It then provides predictions
for the light neutrino with a normal hierarchy and masses such that m{\nu},1
\approx 5\times10-3 eV, m{\nu}, 2 \approx 1\times 10-2 eV, and m{\nu},3 \approx
5 \times 10-2 eV. We also provide predictions for masses of the heavy
neutrinos, and correc- tions to the tri-bimaximal matrix that fit within
experimental limits, e.g. a reactor angle of -7.31o. A simple modification to
our model is introduced at the end and is shown to also produce predictions
that fall well within those limits.Comment: 22 page
Improved Limit on theta_{13} and Implications for Neutrino Masses in Neutrino-less Double Beta Decay and Cosmology
We analyze the impact of a measurement, or of an improved bound, on
theta_{13} for the determination of the effective neutrino mass in
neutrino-less double beta decay and cosmology. In particular, we discuss how an
improved limit on (or a specific value of) theta_{13} can influence the
determination of the neutrino mass spectrum via neutrino-less double beta
decay. We also discuss the interplay with improved cosmological neutrino mass
searches.Comment: 22 pages, 5 figures. Minor corrections, matches version in PR
Researches on the mechanism of induced chromosome rearrangements in Drosophila melanogaster
1) The problem has been investigated as to whether
single breaks induced by irradiation in the chromosomes
of mature sperm of Drosophih /Tazy produce the
loss of whole chromosomes by formation of dicentric
chromosomes originated from lateral fusion of
broken sister chromatids at the point of breakage..The two methods adopted for detecting losses
of X and Y chromosomes and another for detecting
losses of the autosomes are described in detail.2) A dosage experiment (0, 1000, 4000 r) showed that
losses of X and Y are actually produced by irradiation
of the mature sperm, that they are, in part
at least, non lethal to the zygote and that they
occur with a frequency proportional to the first
power of the dosage.3) An experiment in which the frequency of induced
losses was investigated with X and Y chromosomes
of' different cytological length and of different
shape (V shaped and ring shaped) , showed that this
frequency is correlated with the breakage frequency
of the X and Y chromosomes used, and that a ring-shaped
(Xc₂) X-chromosome undergoes loss with a
much higher frequency than a V- or rod-shaped X-chromosome
of the same length.4) Losses of X or Y chromatids, giving origin to
"fractional" (mosaic) flies, in proportion to
chromatid deletions or minute rearrangements,
are less frequent than the corresponding losses of
chromosomes in proportion to chromosome deletions.5) An experiment based on the use of triploids in
which induced losses of the two major autosomes
were investigated; showed that losses of the latter
also, are, under suitable conditions, non-lethal to
the zygote . Their frequency, when losses of one
autosome are compared with that of the other and
also with losses of X and Y, is again suggestive
of a correlation with breakage frequency.6) In the preceding experiment , and in an additional
one made with the purpose of definitely settling
this question, no fly developed in which the loss
of both autosomes or of an X (or Y) and an autosome,
could be attributed to a dicentric translocation
between the chromosomes involved. The
conclusion is drawn that dicentric translocations
are generally, perhaps always, lethal to the zygote
even when, as in the present case, the elimination
of the dicentric would have left the zygote with
a normal diploid set.7) The evidence found is considered as in agreement
with a loss mechanism of the kind suggested in 1).
It is concluded that losses are produced by single
breaks induced by single ionizations along the
chromonema leading to formation of a sister -
chromatid dicentric which either is lost immediately
at first mitotic anaphase or undergoes a
process of repeated breakage which eventually
leads to complete loss.8) To explain why dicentrics of the kind described
in 7) can be eliminated by the zygote in such a way
as to allow /it to survive, while dicentrics formed by fusion
of different chromosomes can not, it is pointed
out that the symmetrical structure of the former as
compared with the asymmetrical of the latter may
account for a different behaviour in mitotic anaphase,
perhaps facilitating, in the latter, the
inclusion of the whole dicentric in one daughter
nucleus instead of its immediate loss through
lagging or repeated breakage.9) It is emphasised that ti-n results found here are
in strong support of the "breakage first" theory
for structural chromosome changes as there is a
direct proportionality to dosage for "single break"
losses in contrast with the proportionality to
about the 1.5 power of the dosage found, within
the range of dosages used here, for gross rearrangements
Constraining Mass Spectra with Sterile Neutrinos from Neutrinoless Double Beta Decay, Tritium Beta Decay and Cosmology
We analyze the constraints on neutrino mass spectra with extra sterile
neutrinos as implied by the LSND experiment. The various mass related
observables in neutrinoless double beta decay, tritium beta decay and cosmology
are discussed. Both neutrino oscillation results as well as recent cosmological
neutrino mass bounds are taken into account. We find that some of the allowed
mass patterns are severely restricted by the current constraints, in particular
by the cosmological constraints on the total sum of neutrino masses and by the
non-maximality of the solar neutrino mixing angle. Furthermore, we estimate the
form of the four neutrino mass matrices and also comment on the situation in
scenarios with two additional sterile neutrinos.Comment: 40 pages, 9 figures. Minor changes, matches version in PR
Lepton number violating four-body tau lepton decays
We study the four-body tau^+- -> nu_tau l^+- l^+- X^-+ decays where l=e or mu
and X=pi, K, rho and K^* mesons. These decay processes violate the total lepton
number (|Delta L|=2) and can be induced by the exchange of Majorana neutrinos.
We consider an scenario where these decays are dominated by the exchange of
only one heavy neutrino which produces an enhancement of the decay amplitude
via the resonant mechanism. Searches for these novel decay channels with
branching fractions sensitivities of (10^-7) can provide constraints on the
parameter space of the Majorana neutrinos which are stronger than the ones
obtained from Delta L=2 decays of charged pseudoscalar mesons.Comment: REVTeX, 14 pages, 6 figures, four references added. Version accepted
for publication in PR
Neutrinoless Double Beta Decay and Future Neutrino Oscillation Precision Experiments
We discuss to what extent future precision measurements of neutrino mixing
observables will influence the information we can draw from a measurement of
(or an improved limit on) neutrinoless double beta decay. Whereas the Delta m^2
corresponding to solar and atmospheric neutrino oscillations are expected to be
known with good precision, the parameter theta_{12} will govern large part of
the uncertainty. We focus in particular on the possibility of distinguishing
the neutrino mass hierarchies and on setting a limit on the neutrino mass. We
give the largest allowed values of the neutrino masses which allow to
distinguish the normal from the inverted hierarchy. All aspects are discussed
as a function of the uncertainty stemming from the involved nuclear matrix
elements. The implications of a vanishing, or extremely small, effective mass
are also investigated. By giving a large list of possible neutrino mass
matrices and their predictions for the observables, we finally explore how a
measurement of (or an improved limit on) neutrinoless double beta decay can
help to identify the neutrino mass matrix if more precise values of the
relevant parameters are known.Comment: 35 pages, 12 figures. Comments and references added. To appear in PR
Quark-lepton mass unification at TeV scales
A scenario combining a model of early (TeV) unification of quarks and leptons
with the physics of large extra dimensions provides a natural mechanism linking
quark and lepton masses at TeV scale. This has been dubbed as early
quark-lepton mass unification by one of us (PQH) in one of the two models of
early quark-lepton unification, which are consistent with data, namely SU(4)_PS
\otimes SU(2)_L \otimes SU(2)_R \otimes SU(2)_H. In particular, it focused on
the issue of naturally light Dirac neutrino. The present paper will focus on
similar issues in the other model, namely SU(4)_PS \otimes SU(3)_L \otimes
SU(3)_H.Comment: Accepted for publication in PRD: The new version is in agreement with
the accepted manuscrip
Neutrino oscillation probabilities: Sensitivity to parameters
We study in detail the sensitivity of neutrino oscillation probabilities to
the fundamental neutrino parameters and their possible determination through
experiments. The first part of the paper is devoted to the broad theme of
isolating regions in the neutrino (and anti-neutrino) energy and propagation
length that are sensitive to the oscillation parameters. Such a study is
relevant to neutrinos both from the Earth's atmosphere or from a neutrino
factory. For completeness we discuss the sensitivity, however small, to the
parameters involved in a three-generation framework, and to the Earth matter
density profile. We then study processes relevant to atmospheric neutrinos
which are sensitive to and allow precision measurements of the mixing angle
theta_23 and mass-squared difference delta_32 apart from the mixing angle
theta_13. Crucial to this analysis is charge identification; detectors having
this capability can isolate these matter effects. In particular, we address the
issue of using matter effects to determine whether the mixing angle theta_23 is
maximal, and, if not, to explore how well its octant can be determined. When
realistic detector resolutions are included, we find that deviations of about
15% (20%) from a maximal value of sin^2 theta_23=1/2 can be measured at 95%
(99%) CL provided theta_13 is non-zero, sin^2 theta_13 >= 0.015, and the
neutrino mass ordering is normal, with fairly large exposures of 1000
kton-years.Comment: 37 pages Latex file, 30 eps figure files; minor typos fixe
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