2,872 research outputs found
Minimally Allowed Neutrinoless Double Beta Decay Rates From Approximate Flavor Symmetries
Neutrinoless double beta decay () is among the only realistic
probes of Majorana neutrinos. In the standard scenario, dominated by light
neutrino exchange, the process amplitude is proportional to , the
element of the Majorana mass matrix. Naively, current data allows for vanishing
, but this should be protected by an appropriate flavor symmetry. All
such symmetries lead to mass matrices inconsistent with oscillation
phenomenology. I perform a spurion analysis to break all possible Abelian
symmetries that guarantee vanishing rates and search for
minimally allowed values. I survey 230 broken structures to yield
values and current phenomenological constraints under a variety of scenarios.
This analysis also extracts predictions for both neutrino oscillation
parameters and kinematic quantities. Assuming reasonable tuning levels, I find
that eV at 99% confidence. Bounds below this value
might indicate the Dirac neutrino nature or the existence of new light (eV-MeV
scale) degrees of freedom that can potentially be probed elsewhere.Comment: 19 Pages, 4 .eps Figures, 3 Table
Not through confusion or fear: motivational approaches for preparing Physician Associate students for post graduate study and beyond.
This is an accepted manuscript of an article published by University of Wolverhampton in Pedagogy in Practice in November 2016, available online: http://ejournal.ewlv.org/?attachment_id=101
The accepted version of the publication may differ from the final published version.This review paper explores the underlying principles of motivating Physician Associate students during both matriculation and progression points of post-graduate study. Pertinent notions of the teacher student relationship and its complexities are examined against the literature, aligned to constructionist learning theories. The impact of such motivational expressions by Higher Education teachers sets the scene for future approaches to deep learning that can impact upon safe and compassionate clinical practice. Educational novices are viewed to be in the ideal position within Higher Education and external stakeholders to explore and design an articulated curriculum that is fit for the 21st century healthcare economies. The correlation between effective motivation and enthusiasm is considered in line with student experiences and expectations resulting in safe effective patient care. The paper suggests that Higher Education teachers would better meet student expectations with more awareness of student entry level behaviour
Deriving Iodine-free spectra for high-resolution echelle spectrographs
We describe a new method to derive clean, iodine-free spectra directly from
observations acquired using high-resolution echelle spectrographs equipped with
iodine cells. The main motivation to obtain iodine-free spectra is to use
portions of the spectrum that are superimposed with the dense forest of iodine
absorption lines, in order to retrieve lines that can be used to monitor the
magnetic activity of the star, helping to validate candidate planets. In short,
we provide a straight-forward methodology to clean the spectra by using the
forward model used to derive radial velocities, the Line Spread Function
information plus the stellar spectrum without iodine to reconstruct and
subtract the iodine spectrum from the observations. We show our results using
observations of the star Ceti acquired with the PFS, HIRES and UCLES
spectrographs, reaching an iodine-free spectrum correction at the 1% RMS
level. We additionally discuss the limitations and further applications of the
method.Comment: 15 pages, 7 figures. Accepted for publication in A
Enskog Theory for Polydisperse Granular Mixtures II. Sonine Polynomial Approximation
The linear integral equations defining the Navier-Stokes (NS) transport
coefficients for polydisperse granular mixtures of smooth inelastic hard disks
or spheres are solved by using the leading terms in a Sonine polynomial
expansion. Explicit expressions for all the NS transport coefficients are given
in terms of the sizes, masses, compositions, density and restitution
coefficients. In addition, the cooling rate is also evaluated to first order in
the gradients. The results hold for arbitrary degree of inelasticity and are
not limited to specific values of the parameters of the mixture. Finally, a
detailed comparison between the derivation of the current theory and previous
theories for mixtures is made, with attention paid to the implication of the
various treatments employed to date.Comment: 26 pages, to be published in Phys. Rev.
A Survey of Lepton Number Violation Via Effective Operators
We survey 129 lepton number violating effective operators, consistent with
the minimal Standard Model gauge group and particle content, of mass dimension
up to and including eleven. Upon requiring that each one radiatively generates
the observed neutrino masses, we extract an associated characteristic cutoff
energy scale which we use to calculate other observable manifestations of these
operators for a number of current and future experimental probes, concentrating
on lepton number violating phenomena. These include searches for neutrinoless
double-beta decay and rare meson, lepton, and gauge boson decays. We also
consider searches at hadron/lepton collider facilities in anticipation of the
LHC and the future ILC. We find that some operators are already disfavored by
current data, while more are ripe to be probed by next-generation experiments.
We also find that our current understanding of lepton mixing disfavors a subset
of higher dimensional operators. While neutrinoless double-beta decay is the
most promising signature of lepton number violation for the majority of
operators, a handful is best probed by other means. We argue that a combination
of constraints from various independent experimental sources will help to
pinpoint the ``correct'' model of neutrino mass, or at least aid in narrowing
down the set of possibilities.Comment: 34 pages, 10 eps figures, 1 tabl
SPECIES II. Stellar parameters of the EXPRESS program giant star sample
As part of the search for planets around evolved stars, we can understand
planet populations around significantly higher-mass stars than the Sun on the
main sequence. This population is difficult to study any other way,
particularly with radial-velocities since these stars are too hot and rotate
too fast to measure precise velocities. Here we estimate stellar parameters for
all of the giant stars from the EXPRESS project, which aims to detect planets
orbiting evolved stars, and study their occurrence rate as a function of
stellar mass. We analyse high resolution echelle spectra of these stars, and
compute the atmospheric parameters by measuring the equivalent widths for a set
of iron lines, using an updated method implemented during this work. Physical
parameters are computed by interpolating through a grid of stellar evolutionary
models, following a procedure that carefully takes into account the post-MS
evolutionary phases. Probabilities of the star being in the red giant branch
(RBG) or the horizontal branch (HB) are estimated from the derived
distributions. Results: We find that, out of 166 evolved stars, 101 of them are
most likely in the RGB phase, while 65 of them are in the HB phase. The mean
derived mass is 1.41 and 1.87 Msun for RGB and HB stars, respectively. To
validate our method, we compared our results with interferometry and
asteroseismology studies. We find a difference in the radius with
interferometry of 1.7%. With asteroseismology, we find 2.4% difference in logg,
1.5% in radius, 6.2% in mass, and 11.9% in age. Compared with previous
spectroscopic studies, and find a 0.5% difference in Teff, 1% in logg, and 2%
in [Fe/H]. We also find a mean mass difference with respect to the EXPRESS
original catalogue of 16%. We show that the method presented here can greatly
improve the estimates of the stellar parameters for giant stars compared to
what was presented previously.Comment: 24 pages, 17 figures, 15 tables, accepted by A&
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