722 research outputs found
Large Mixing Induced by the Strong Coupling with a Single Bulk Neutrinos
Neutrino is a good probe of extra dimensions. Large mixing and the apparent
lack of very complicated oscillation patterns may be an indication of large
couplings between the brane and a single bulk neutrino. A simple and realistic
five-dimensional model of this kind is discussed. It requires a sterile in
addition to three active neutrinos on the brane, all coupled strongly to one
common bulk neutrino, but not directly among themselves. Mindful that sterile
neutrinos are disfavored in the atmospheric and solar data, we demand induced
mixing to occur among the active neutrinos, but not between the active and the
sterile. The size of the extra dimension is arbitrary in this model,
otherwise it contains six parameters which can be used to fit the three
neutrino masses and the three mixing angles. However, in the model those six
parameters must be suitably ordered, so a successful fit is not guaranteed. It
turns out that not only the data can be fitted, but as a result of the
ordering, a natural connection between the smallness of the reactor angle
and the smallness of the mass-gap ratio can be derived.Comment: Misprints above eq. (22) corrected. To appear in PR
Lepton Masses and Mixing in a Left-Right Symmetric Model with a TeV-scale Gravity
We construct a left-right symmetric (LRS) model in five dimensions which
accounts naturally for the lepton flavor parameters. The fifth dimension is
described by an orbifold, S_1/Z_2 times Z'_2, with a typical size of order
TeV^{-1}. The fundamental scale is of order 25 TeV which implies that the gauge
hierarchy problem is ameliorated. In addition the LRS breaking scale is of
order few TeV which implies that interactions beyond those of the standard
model are accessible to near future experiments. Leptons of different
representations are localized around different orbifold fixed points. This
explains, through the Arkani-Hamed-Schmaltz mechanism, the smallness of the tau
mass compared to the electroweak breaking scale. An additional U(1) horizontal
symmetry, broken by small parameters, yields the hierarchy in the charged
lepton masses, strong suppression of the light neutrino masses and accounts for
the mixing parameters. The model yields several unique predictions. In
particular, the branching ratio for the lepton flavor violating process mu^-
--> e^+ e^- e^- is comparable with its present experimental sensitivity.Comment: 21 pages, 1 figure, references added, discussion on the
predictiveness of the model in the generic non-universal case added, to
appear in PR
Flavor Ratios of Astrophysical Neutrinos: Implications for Precision Measurements
We discuss flavor-mixing probabilities and flavor ratios of high energy
astrophysical neutrinos. In the first part of this paper, we expand the
neutrino flavor-fluxes in terms of the small parameters U_{e3} and pi/4 -
theta_{23}, and show that there are universal first and second order
corrections. The second order term can exceed the first order term, and so
should be included in any analytic study. We also investigate the probabilities
and ratios after a further expansion around the tribimaximal value of sin^2
theta_{12} = 1/3. In the second part of the paper, we discuss implications of
deviations of initial flavor ratios from the usually assumed, idealized flavor
compositions for pion, muon-damped, and neutron beam sources, viz., (1 : 2 :
0), (0 : 1 : 0), and (1 : 0 : 0), respectively. We show that even small
deviations have significant consequences for the observed flavor ratios at
Earth. If initial flavor deviations are not taken into account in analyses,
then false inferences for the values in the PMNS matrix elements (angles and
phase) may result.Comment: 32 pages, 15 figures. Minor changes, matches version in JHE
Leptogenesis and low energy observables in left-right symmetric models
In the context of left-right symmetric models we study the connection of
leptogenesis and low energy parameters such as neutrinoless double beta decay
and leptonic CP violation. Upon imposition of a unitarity constraint, the
neutrino parameters are significantly restricted and the Majorana phases are
determined within a narrow range, depending on the kind of solar solution. One
of the Majorana phases gets determined to a good accuracy and thereby the
second phase can be probed from the results of neutrinoless double beta decay
experiments. We examine the contributions of the solar and atmospheric mass
squared differences to the asymmetry and find that in general the solar scale
dominates. In order to let the atmospheric scale dominate, some finetuning
between one of the Majorana phases and the Dirac CP phase is required. In this
case, one of the Majorana phases is determined by the amount of CP violation in
oscillation experiments.Comment: 18 pages, 6 figures. Matches version to appear in PR
Minimal SUSY SO(10) model and predictions for neutrino mixings and leptonic CP violation
We discuss a minimal Supersymmetric SO(10) model where B-L symmetry is broken
by a {\bf 126} dimensional Higgs multiplet which also contributes to fermion
masses in conjunction with a {\bf 10} dimensional superfield. This minimal
Higgs choice provides a partial unification of neutrino flavor structure with
that of quarks and has been shown to predict all three neutrino mixing angles
and the solar mass splitting in agreement with observations, provided one uses
the type II seesaw formula for neutrino masses. In this paper we generalize
this analysis to include arbitrary CP phases in couplings and vevs. We find
that (i) the predictions for neutrino mixings are similar with as before and other parameters in a somewhat bigger range and (ii) that
to first order in the quark mixing parameter (the Cabibbo angle), the
leptonic mixing matrix is CP conserving. We also find that in the absence of
any higher dimensional contributions to fermion masses, the CKM phase is
different from that of the standard model implying that there must be new
contributions to quark CP violation from the supersymmetry breaking sector.
Inclusion of higher dimensional terms however allows the standard model CKM
phase to be maintained.Comment: 22 pages, 6 figure
Mental Health Risk and Associated Factors in the Aftermath of the 2015 Earthquake in Nepal: A Systematic Literature Review
Background: In 2015, Nepal was struck by two massive earthquakes with magnitudes over the 7.0 Richter Scale, imposing short- and long-term mental health risks. This review aims to: (a) evaluate mental health risk among the earthquake survivors; and, (b) identify factors that influence it. Methods: The following databases: Scopus and PubMed were searched to identify studies published from 2015 to July 2020 on the mental health risk among the Nepali populations. Inclusion criteria were: (a) primary research related to mental health after the 2015 earthquakes in Nepal, (b) English language articles, (c) access to full-text literature, and (d) studies conducted on the general population of Nepal. Exclusion criteria were: (a) newspaper articles or other forms of popular media, (b) grey records and reviews or, (c) studies carried out among patients in a clinical setting. Key features and risk of bias factors were extracted from each study to obtain necessary characteristics for further analysis of results. Results: The initial search produced 134 articles, however, a total, 14 studies fulfilled the inclusion criteria and were explored for this review. Ten of these articles were obtained from established databases, and four additional studies were obtained from other sources. Findings indicate that post-traumatic stress was mostly present among earthquake survivors with rates varying from 4.9% to 51%. Mental health risks for children and adolescent were mostly high with rates greater than 23% across studies. However, the adult prevalence rate for mental health risk was lower than that of children and adolescents, with most rates across studies lower than 20%. Socio-demographic factors (such as gender and age) and methodological heterogeneities such as variations in study design and mental health tools used to assess rates were associated factors that potentially influenced the findings. Conclusion: Mental health risks are present among earthquake survivors in Nepal. Various factors have been identified as potential mental health risk rate influencers including sex, with females presenting as the higher at-risk group for mental health relative to males. Methodological issues such as a wide range of mental health assessment instruments employed across studies can potentially impact rates
Bi-large Neutrino Mixing and Mass of the Lightest Neutrino from Third Generation Dominance in a Democratic Approach
We show that both small mixing in the quark sector and large mixing in the
lepton sector can be obtained from a simple assumption of universality of
Yukawa couplings and the right-handed neutrino Majorana mass matrix in leading
order. We discuss conditions under which bi-large mixing in the lepton sector
is achieved with a minimal amount of fine-tuning requirements for possible
models. From knowledge of the solar and atmospheric mixing angles we determine
the allowed values of sin \theta_{13}. If embedded into grand unified theories,
the third generation Yukawa coupling unification is a generic feature while
masses of the first two generations of charged fermions depend on small
perturbations. In the neutrino sector, the heavier two neutrinos are model
dependent, while the mass of the lightest neutrino in this approach does not
depend on perturbations in the leading order. The right-handed neutrino mass
scale can be identified with the GUT scale in which case the mass of the
lightest neutrino is given as (m_{top}^2/M_{GUT}) sin^2 \theta_{23} sin^2
\theta_{12} in the limit sin \theta_{13} = 0. Discussing symmetries we make a
connection with hierarchical models and show that the basis independent
characteristic of this scenario is a strong dominance of the third generation
right-handed neutrino, M_1, M_2 < 10^{-4} M_3, M_3 = M_{GUT}.Comment: typos correcte
The SUSY seesaw model and lepton-flavor violation at a future electron-positron linear collider
We study lepton-flavor violating slepton production and decay at a future
e^+e^- linear collider in context with the seesaw mechanism in mSUGRA post-LEP
benchmark scenarios. The present knowledge in the neutrino sector as well as
improved future measurements are taken into account. We calculate the signal
cross-sections \sigma(e^{+/-}e^- -> l_{\beta}^{+/-} l_{\alpha}^-
\tilde{\chi}_b^0 \tilde{\chi}_a^0); l_{\delta}=e, \mu, \tau; \alpha =|= \beta
and estimate the main background processes. Furthermore, we investigate the
correlations of these signals with the corresponding lepton-flavor violating
rare decays l_{\alpha} -> l_{\beta} \gamma. It is shown that these correlations
are relatively weakly affected by uncertainties in the neutrino data, but very
sensitive to the model parameters. Hence, they are particularly suited for
probing the origin of lepton-flavor violation.Comment: 31 pages, 10 figures, version published in Phys. Rev.
Spatial correlations in vote statistics: a diffusive field model for decision-making
We study the statistics of turnout rates and results of the French elections
since 1992. We find that the distribution of turnout rates across towns is
surprisingly stable over time. The spatial correlation of the turnout rates, or
of the fraction of winning votes, is found to decay logarithmically with the
distance between towns. Based on these empirical observations and on the
analogy with a two-dimensional random diffusion equation, we propose that
individual decisions can be rationalised in terms of an underlying "cultural"
field, that locally biases the decision of the population of a given region, on
top of an idiosyncratic, town-dependent field, with short range correlations.
Using symmetry considerations and a set of plausible assumptions, we suggest
that this cultural field obeys a random diffusion equation.Comment: 18 pages, 5 figures; added sociophysics references
Muon Anomalous Magnetic Moment and mu -> e gamma in B-L Model with Inverse Seesaw
We study the anomalous magnetic moment of the muon, a_\mu, and lepton flavor
violating decay \mu -> e \gamma in TeV scale B-L extension of the Standard
Model (SM) with inverse seesaw mechanism. We show that the B-L contributions to
a_\mu are severely constrained, therefore the SM contribution remains intact.
We also emphasize that the current experimental limit of BR(\mu -> e \gamma)
can be satisfied for a wide range of parameter space and it can be within the
reach of MEG experiment.Comment: 10 pages, 4 Figure
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