224 research outputs found
Fourth Lepton Family is Natural in Technicolor
Imagine to discover a new fourth family of leptons at the Large Hadron
Collider (LHC) but no signs of an associated fourth family of quarks. What
would that imply? An intriguing possibility is that the new fermions needed to
compensate for the new leptons gauge anomalies simultaneously address the big
hierarchy problem of the Standard Model. A natural way to accomplish such a
scenario is to have the Higgs itself be composite of these new fermions. This
is the setup we are going to investigate in this paper using as a template
Minimal Walking Technicolor. We analyze a general heavy neutrino mass structure
with and without mixing with the Standard Model families. We also analyze the
LHC potential to observe the fourth lepton family in tandem with the new
composite Higgs dynamics. We finally introduce a model uniting the fourth
lepton family and the technifermion sector at higher energies.Comment: 39 ReVTeX pages, 16 figure
Looking for a charge asymmetry in cosmic rays
We combine the data from PAMELA and FERMI-LAT cosmic ray experiments by
introducing a simple sum rule. This allows to investigate whether the lepton
excess observed by these experiments is charge symmetric or not. We also show
how the data can be used to predict the positron fraction at energies yet to be
explored by the AMS-02 experiment.Comment: Contribution to the proceedings of DISCRETE 2010, 5 pages, 2 figure
Cosmic Sum Rules
We introduce new sum rules allowing to determine universal properties of the
unknown component of the cosmic rays and show how they can be used to predict
the positron fraction at energies not yet explored by current experiments and
to constrain specific models.Comment: RevTeX, 4 pages, 6 figures, two-columns. Final version to match the
published version in Brief Reports section of Phys. Rev. D. We stress that
this is the first paper about charge asymmetries in cosmic ray
Factors affecting VBAC success at a tertiary level Hospital in Pretoria, South Africa
There is growing concern about rising global caesarean delivery (CD) rates. One of the strategies to overcome this problem is
to reduce primary caesarean section. A trial of labour following a previous CD is another option that may be explored.
AIM
The aim of the study was to determine the success rate and risk factors for women attempting vaginal birth after a prior
caesarean delivery (VBAC).
METHODS
This was a retrospective analysis from 2013-2018 of women attempting a vaginal birth after caesarean section at a tertiary
level hospital in Pretoria, South Africa.
RESULTS
The VBAC success rate was 36%. Factors that were associated with a successful VBAC were a third pregnancy, previous
successful VBAC (61%), presentation in the active phase of labour and a neonatal birthweight of less than 3kg.
CONCLUSION
Pregnant women with a CD in a prior pregnancy should be appropriately counselled regarding delivery options. Risks and
benefi ts of elective repeat caesarean delivery versus trial of labour should be clearly explained to expectant mothers.http://reference.sabinet.co.za/sa_epublication/medoghttps://journals.co.za/journal/medogam2022Obstetrics and Gynaecolog
Global Mean Climate and Main Patterns of Variability in the CMCC-CM2 Coupled Model
Euro-Mediterranean Centre on Climate Change coupled climate model (CMCC-CM2) represents the new family of the global coupled climate models developed and used at CMCC. It is based on the atmospheric, land and sea ice components from the Community Earth System Model coupled with the global ocean model Nucleus for European Modeling of the Ocean. This study documents the model components, the coupling strategy, particularly for the oceanic, atmospheric, and sea ice components, and the overall model ability in reproducing the observed mean climate and main patterns of interannual variability. As a first step toward a more comprehensive, process-oriented, validation of the model, this work analyzes a 200-year simulation performed under constant forcing corresponding to present-day climate conditions. In terms of mean climate, the model is able to realistically reproduce the main patterns of temperature, precipitation, and winds. Specifically, we report improvements in the representation of the sea surface temperature with respect to the previous version of the model. In terms of mean atmospheric circulation features, we notice a realistic simulation of upper tropospheric winds and midtroposphere geopotential eddies. The oceanic heat transport and the Atlantic meridional overturning circulation satisfactorily compare with present-day observations and estimates from global ocean reanalyses. The sea ice patterns and associated seasonal variations are realistically reproduced in both hemispheres, with a better skill in winter. Main weaknesses of the simulated climate are related with the precipitation patterns, specifically in the tropical regions with large dry biases over the Amazon basin. Similarly, the seasonal precipitation associated with the monsoons, mostly over Asia, is weaker than observed. The main patterns of interannual variability in terms of dominant empirical orthogonal functions are faithfully reproduced, mostly in the Northern Hemisphere winter. In the tropics the main teleconnection patterns associated with El Nino-Southern Oscillation and with the Indian Ocean Dipole are also in good agreement with observations
Repressing Anarchy in Neutrino Mass Textures
The recent results that is relatively large, of the order of
the previous upper bound, and the indications of a sizable deviation of
from the maximal value are in agreement with the predictions of
Anarchy in the lepton sector. The quark and charged lepton hierarchies can then
be reproduced in a SU(5) GUT context by attributing non-vanishing
charges, different for each family, only to the SU(5) tenplet states. The fact
that the observed mass hierarchies are stronger for up quarks than for down
quarks and charged leptons supports this idea. As discussed in the past, in the
flexible context of , different patterns of charges can
be adopted going from Anarchy to various types of hierarchy. We revisit this
approach by also considering new models and we compare all versions to the
present data. As a result we confirm that, by relaxing the extreme ansatz of
equal charges for all SU(5) pentaplets and singlets, better
agreement with the data than for Anarchy is obtained without increasing the
model complexity. We also present the distributions obtained in the different
models for the Dirac CP-violating phase. Finally we discuss the relative merits
of these simple models.Comment: v1: 12 pages, 3 figures; v2: 13 pages, 3 figures, text improved,
matches version accepted for publication; v3: submitted to add an
acknowledgment to a networ
Minimal Scenarios for Leptogenesis and CP Violation
The relation between leptogenesis and CP violation at low energies is
analyzed in detail in the framework of the minimal seesaw mechanism. Working,
without loss of generality, in a weak basis where both the charged lepton and
the right-handed Majorana mass matrices are diagonal and real, we consider a
convenient generic parametrization of the Dirac neutrino Yukawa coupling matrix
and identify the necessary condition which has to be satisfied in order to
establish a direct link between leptogenesis and CP violation at low energies.
In the context of the LMA solution of the solar neutrino problem, we present
minimal scenarios which allow for the full determination of the cosmological
baryon asymmetry and the strength of CP violation in neutrino oscillations.
Some specific realizations of these minimal scenarios are considered. The
question of the relative sign between the baryon asymmetry and CP violation at
low energies is also discussed.Comment: 36 pages, 5 figures; minor corrections and references updated. Final
version to appear in Phys. Rev.
Testing new physics with the electron g-2
We argue that the anomalous magnetic moment of the electron (a_e) can be used
to probe new physics. We show that the present bound on new-physics
contributions to a_e is 8*10^-13, but the sensitivity can be improved by about
an order of magnitude with new measurements of a_e and more refined
determinations of alpha in atomic-physics experiments. Tests on new-physics
effects in a_e can play a crucial role in the interpretation of the observed
discrepancy in the anomalous magnetic moment of the muon (a_mu). In a large
class of models, new contributions to magnetic moments scale with the square of
lepton masses and thus the anomaly in a_mu suggests a new-physics effect in a_e
of (0.7 +- 0.2)*10^-13. We also present examples of new-physics theories in
which this scaling is violated and larger effects in a_e are expected. In such
models the value of a_e is correlated with specific predictions for processes
with violation of lepton number or lepton universality, and with the electric
dipole moment of the electron.Comment: 34 pages, 7 figures. Minor changes and references adde
Models of Neutrino Masses: Anarchy versus Hierarchy
We present a quantitative study of the ability of models with different
levels of hierarchy to reproduce the solar neutrino solutions, in particular
the LA solution. As a flexible testing ground we consider models based on
SU(5)xU(1)_F. In this context, we have made statistical simulations of models
with different patterns from anarchy to various types of hierachy: normal
hierarchical models with and without automatic suppression of the 23
(sub)determinant and inverse hierarchy models. We find that, not only for the
LOW or VO solutions, but even in the LA case, the hierarchical models have a
significantly better success rate than those based on anarchy. The normal
hierachy and the inverse hierarchy models have comparable performances in
models with see-saw dominance, while the inverse hierarchy models are
particularly good in the no see-saw versions. As a possible distinction between
these categories of models, the inverse hierarchy models favour a maximal solar
mixing angle and their rate of success drops dramatically as the mixing angle
decreases, while normal hierarchy models are far more stable in this respect.Comment: v1: 28 pages, 12 figures; v2: 34 pages, 14 figures, updated previous
analysis with the inclusion of recent SNO result
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