419 research outputs found
Revelations of the E_6/U(1)_N Model: Two-Loop Neutrino Mass and Dark Matter
The E_6/U(1)_N gauge extension of the Supersymmetric Standard Model, first
proposed by Ma, is shown to have exactly the requisite ingredients to realize
the important new idea that dark matter is the origin of neutrino mass. With
the implementation of a discrete Z_2 X Z_2 symmetry, and particle content given
by three {27} representations of E_6, neutrino masses are naturally generated
in two loops, with candidates of dark matter in the loops. All particles of
this model are expected to be at or below the TeV scale, allowing them to be
observable at the LHC.Comment: 10 pages, 3 figure
Neutral SU(2) Gauge Extension of the Standard Model and a Vector-Boson Dark-Matter Candidate
If the standard model of particle interactions is extended to include a
neutral SU(2)_N gauge factor, with SU(3)_C x SU(2)_L x U(1)_Y x SU(2)_N
embedded in E_6 or [SU(3)]^3, a conserved generalized R parity may appear. As a
result, we have the first example of a possible dark-matter candidate X_1 which
is a non-Abelain vector boson. Using current data, its mass is predicted to be
less than about 1 TeV. The associated Z' of this model, as well as some
signatures of the Higgs sector, should then be observable at the LHC (Large
Hadron Collider).Comment: 10 pages, 1 figure; version accepted in PL
Z_3 Dark Matter and Two-Loop Neutrino Mass
Dark matter is usually distinguished from ordinary matter by an odd-even
parity, i.e. the discrete symmetry Z_2. The new idea of Z_3 dark matter is
proposed with a special application to generating radiative Majorana neutrino
masses in two-loop order.Comment: expanded (9 pages, 2 figures), 2 references adde
Cold Dark Matter, Radiative Neutrino Mass, mu to e gamma, and Neutrinoless Double Beta Decay
Two of the most important and pressing questions in cosmology and particle
physics are: (1) What is the nature of cold dark matter? and (2) Will
near-future experiments on neutrinoless double beta decay be able to ascertain
that the neutrino is a Majorana particle, i.e. its own antiparticle? We show
that these two seemingly unrelated issues are intimately connected if neutrinos
acquire mass only because of their interactions with dark matter.Comment: 12 pages, 5 figure
Associations of Daily Eating Episodes, and Eating Away-from-home with Blood Level of Total Cholesterol
The objective of this investigation is to describe the associations of number of eating episodes and proportion of meals eaten away from home with total serum cholesterol. Data from 499 participants, recruited from a health maintenance organization in central Massachusetts, aged 20-70, were used for this analysis. Dietary information and total blood cholesterol were obtained at five sampling points (baseline and four consecutive quarters) during the one-year follow-up. A cross-sectional study was conducted. The results from the study do not support the hypothesis that the number of eating episodes per day is associated with total blood cholesterol. However, we noted that the mean concentration of total cholesterol decreased with increasing number of eating episodes among women, although the adjusted mean among three categories of number of eating episodes per day was not statistically significant. On the other hand, the results of our study suggest that increased frequency of meals (breakfast, lunch, or dinner) eaten away from home is positively associated with mean total blood cholesterol concentration. Furthermore, meals eaten away from home, especially breakfast and dinner, were significantly higher in total calories, and percent calories from total and saturated fat, but lower in percent calories from protein and carbohydrate, and grams of fiber, than corresponding meals eaten at home. We conclude that eating out may have adverse influences on blood lipids. Further research is needed to better understand the impact of eating away from home on blood lipids
Pure Leptonic Gauge Symmetry, Neutrino Masses and Dark Matter
A possible extension of the Standard Model to include lepton number as local
gauge symmetry is investigated. In such a model, anomalies are canceled by two
extra fermions doublet. After leptonic gauge symmetry spontaneously broken,
three active neutrinos may acquire non-zero Majorana masses through the
modified Type-II seesaw mechanism. Constraints on the model from electro-weak
precision measurements are studied. Due to the discrete flavor symmetry,
right-handed Majorana neutrinos can serve as cold dark matter candidate of the
Universe. Constraint from dark matter relic abundance is calculated.Comment: 13 pages, 2 figures; typos corrected, comments and references added,
to appear in Phys. Lett.
Accidental stability of dark matter
We propose that dark matter is stable as a consequence of an accidental Z2
that results from a flavour-symmetry group which is the double-cover group of
the symmetry group of one of the regular geometric solids. Although
model-dependent, the phenomenology resembles that of a generic Higgs portal
dark matter scheme.Comment: 12 pages, final version, published in JHE
Ecology of Sleeping: The Microbial and Arthropod Associates of Chimpanzee Beds
The indoor environment created by the construction of homes and other buildings is often considered to be uniquely different from other environments. It is composed of organisms that are less diverse than those of the outdoors and strongly sourced by, or dependent upon, human bodies. Yet, no one has ever compared the composition of species found in contemporary human homes to that of other structures built by mammals, including those of non-human primates. Here we consider the microbes and arthropods found in chimpanzee beds, relative to the surrounding environment (n = 41 and 15 beds, respectively). Based on the study of human homes, we hypothesized that the microbes found in chimpanzee beds would be less diverse than those on nearby branches and leaves and that their beds would be primarily composed of body-associated organisms. However, we found that differences between wet and dry seasons and elevation above sea level explained nearly all of the observed variation in microbial diversity and community structure. While we can identify the presence of a chimpanzee based on the assemblage of bacteria, the dominant signal is that of environmental microbes. We found just four ectoparasitic arthropod specimens, none of which appears to be specialized on chimpanzees or their structures. These results suggest that the life to which chimpanzees are exposed while in their beds is predominately the same as that of the surrounding environment
Increased Sensitivity to Mirror Symmetry in Autism
Can autistic people see the forest for the trees? Ongoing uncertainty about the integrity and role of global processing in autism gives special importance to the question of how autistic individuals group local stimulus attributes into meaningful spatial patterns. We investigated visual grouping in autism by measuring sensitivity to mirror symmetry, a highly-salient perceptual image attribute preceding object recognition. Autistic and non-autistic individuals were asked to detect mirror symmetry oriented along vertical, oblique, and horizontal axes. Both groups performed best when the axis was vertical, but across all randomly-presented axis orientations, autistics were significantly more sensitive to symmetry than non-autistics. We suggest that under some circumstances, autistic individuals can take advantage of parallel access to local and global information. In other words, autistics may sometimes see the forest and the trees, and may therefore extract from noisy environments genuine regularities which elude non-autistic observers
Neutrino Masses, Dark Matter and B-L Symmetry at the LHC
We establish a hybrid seesaw mechanism to explain small neutrino masses and
predict cold dark matter candidate in the context of the B-L gauge symmetry
extension of the Standard Model. In this model a new scalar doublet and two new
fermion singlets are introduced at loop-level beyond the minimal Type I seesaw.
The lightest particle inside the loop can be dark matter candidate. We study in
detail the constraints from neutrino oscillation data, lepton flavor violating
processes and cosmological observation. We also explore the predictions of the
decays of the new charged scalars in each spectrum of neutrino masses and show
the most optimistic scenarios to distinguish the spectra. We consider the pair
production of the stable fermion associated with two observable SM charged
leptons at the LHC, which occurs in a two-step cascade decay of the new gauge
boson Z' and the new charged scalars stand as intermediate particles. The
masses of missing dark matter and its parent particle can be well-determined in
such production topology.Comment: 20 pages, 9 figures and 2 tables, revised version accepted for
publication in Nucl. Phys.
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