306 research outputs found
Phenomenology of quintessino dark matter -- Production of NLSP particles
In the model of quintessino as dark matter particle, the dark matter and dark
energy are unified in one superfield, where the dynamics of the Quintessence
drives the Universe acceleration and its superpartner, quintessino, makes up
the dark matter of the Universe. This scenario predicts the existence of long
lived as the next lightest supersymmetric particle. In this
paper we study the possibility of detecting produced by the high
energy cosmic neutrinos interacting with the earth matter. By a detailed
calculation we find that the event rate is one to several hundred per year at a
detector with effective area of . The study in this paper can be also
applied for models of gravitino or axino dark matter particles.Comment: 16 pages, 5 figures, a new section about NLSP stau is added,
references adde
Neutrino Telescopes as a Direct Probe of Supersymmetry Breaking
We consider supersymmetric models where the scale of supersymmetry breaking
lies between 5 GeV and 5 GeV. In this class of
theories, which includes models of gauge mediated supersymmetry breaking, the
lightest supersymmetric particle is the gravitino. The next to lightest
supersymmetric particle is typically a long lived charged slepton with a
lifetime between a microsecond and a second, depending on its mass. Collisions
of high energy neutrinos with nucleons in the earth can result in the
production of a pair of these sleptons. Their very high boost means they
typically decay outside the earth. We investigate the production of these
particles by the diffuse flux of high energy neutrinos, and the potential for
their observation in large ice or water Cerenkov detectors. The relatively
small cross-section for the production of supersymmetric particles is partially
compensated for by the very long range of heavy particles. The signal in the
detector consists of two parallel charged tracks emerging from the earth about
100 meters apart, with very little background. A detailed calculation using the
Waxman-Bahcall limit on the neutrino flux and realistic spectra shows that
km experiments could see as many as 4 events a year. We conclude that
neutrino telescopes will complement collider searches in the determination of
the supersymmetry breaking scale, and may even give the first evidence for
supersymmetry at the weak scale.Comment: 4 pages, 3 figure
Charged Higgs boson contribution to for very large in the two Higgs doublet model with UHE-neutrinos
We study the deep inelastic process
(with an isoscalar nucleon), in the context of the
two Higgs doublet model {\it type two} (2HDM(II)). In particular, we discuss
the contribution to the total cross section of diagrams, in which a charged
Higgs boson is exchanged. We show that for large values of such
contribution for an inclusive dispersion generated through the collision of an
ultrahigh energy tau-neutrino on a target nucleon can reach up to 57% of the
value of the contribution of the exchange diagrams (i.e. can reach up to
57% of the standard model (SM) prediction) and could permit to distinguish
between the SM and the 2HDM(II) predictions at the Pierre Auger Observatory.Comment: 10 pages, 5 figure
Radiation in Lorentz violating electrodynamics
Synchrotron radiation is analyzed in the classical effective Lorentz
invariance violating model of Myers-Pospelov. Within the full far-field
approximation we compute the electric and magnetic fields, the angular
distribution of the power spectrum and the total emitted power in the m-th
harmonic, as well as the polarization. We find the appearance of rather
unexpected and large amplifying factors, which go together with the otherwise
negligible naive expansion parameter. This opens up the possibility of further
exploring Lorentz invariance violations by synchrotron radiation measurements
in astrophysical sources where these amplifying factors are important.Comment: Presented at the Second Mexican Meeting on Theoretical and
Experimental Physics, El Colegio Nacional, Mexico City, 6-10 September 200
Default Mode Network Complexity and Cognitive Decline in Mild Alzheimer’s Disease
The human resting-state is characterized by spatially coherent brain activity at a low temporal frequency. The default mode network (DMN), one of so-called resting-state networks, has been associated with cognitive processes that are directed toward the self, such as introspection and autobiographic memory. The DMN’s integrity appears to be crucial for mental health. For example, patients with Alzheimer’s disease or other psychiatric conditions show disruptions of functional connectivity within the brain regions of the DMN. However, in prodromal or early stages of Alzheimer’s disease, physiological alterations are sometimes elusive, despite manifested cognitive impairment. While functional connectivity assesses the signal correlation between brain areas, multi-scale entropy (MSE) measures the complexity of the blood-oxygen level dependent signal within an area and thus might show local changes before connectivity is affected. Hence, we investigated alterations of functional connectivity and MSE within the DMN in fifteen mild Alzheimer’s disease patients as compared to fourteen controls. Potential associations of MSE with functional connectivity and cognitive abilities [i.e., mini-mental state examination (MMSE)] were assessed. A moderate decrease of DMN functional connectivity between posterior cingulate cortex and right hippocampus in Alzheimer’s disease was found, whereas no differences were evident for whole-network functional connectivity. In contrast, the Alzheimer’s disease group yielded lower global DMN-MSE than the control group. The most pronounced regional effects were localized in left and right hippocampi, and this was true for most scales. Moreover, MSE significantly correlated with functional connectivity, and DMN-MSE correlated positively with the MMSE in Alzheimer’s disease. Most interestingly, the right hippocampal MSE was positively associated with semantic memory performance. Thus, our results suggested that cognitive decline in Alzheimer’s disease is reflected by decreased signal complexity in DMN nodes, which might further lead to disrupted DMN functional connectivity. Additionally, altered entropy in Alzheimer’s disease found in the majority of the scales indicated a disturbance of both local information processing and information transfer between distal areas. Conclusively, a loss of nodal signal complexity potentially impairs synchronization across nodes and thus preempts functional connectivity changes. MSE presents a putative functional marker for cognitive decline that might be more sensitive than functional connectivity alone
Possible High-energy neutrinos from the cosmic accelerator RXJ1713.7-3946
The observation of TeV-gamma rays of neutral pion origin from the supernova
remnant RX J1713.7-3946 might have revealed the first specific site where
protons are accelerated to energies typical of the main component of the cosmic
rays. In this letter we calculate the high-energy neutrino flux associated with
this source to be at least 40 muon-type neutrinos per kilometer-squared per
year. We perform the same calculations for other known sources of TeV-gamma
rays and show how neutrino observations can establish whether the TeV-gamma
rays emitted by blazars and supernova remnants are the decay products of
neutral pions and thus unequivocally establish the sources as cosmic
accelerators.Comment: Replaced with version published in Astrophys.
Measurements of integral muon intensity at large zenith angles
High-statistics data on near-horizontal muons collected with Russian-Italian
coordinate detector DECOR are analyzed. Precise measurements of muon angular
distributions in zenith angle interval from 60 to 90 degrees have been
performed. In total, more than 20 million muons are selected. Dependences of
the absolute integral muon intensity on zenith angle for several threshold
energies ranging from 1.7 GeV to 7.2 GeV are derived. Results for this region
of zenith angles and threshold energies have been obtained for the first time.
The dependence of integral intensity on zenith angle and threshold energy is
well fitted by a simple analytical formula.Comment: 4 pages, 4 figures, 1 tabl
Features of Muon Arrival Time Distributions of High Energy EAS at Large Distances From the Shower Axis
In view of the current efforts to extend the KASCADE experiment
(KASCADE-Grande) for observations of Extensive Air Showers (EAS) of primary
energies up to 1 EeV, the features of muon arrival time distributions and their
correlations with other observable EAS quantities have been scrutinised on
basis of high-energy EAS, simulated with the Monte Carlo code CORSIKA and using
in general the QGSJET model as generator. Methodically various correlations of
adequately defined arrival time parameters with other EAS parameters have been
investigated by invoking non-parametric methods for the analysis of
multivariate distributions, studying the classification and misclassification
probabilities of various observable sets. It turns out that adding the arrival
time information and the multiplicity of muons spanning the observed time
distributions has distinct effects improving the mass discrimination. A further
outcome of the studies is the feature that for the considered ranges of primary
energies and of distances from the shower axis the discrimination power of
global arrival time distributions referring to the arrival time of the shower
core is only marginally enhanced as compared to local distributions referring
to the arrival of the locally first muon.Comment: 24 pages, Journal Physics G accepte
Lateral Gene Expression in Drosophila Early Embryos Is Supported by Grainyhead-Mediated Activation and Tiers of Dorsally-Localized Repression
The general consensus in the field is that limiting amounts of the transcription factor Dorsal establish dorsal boundaries of genes expressed along the dorsal-ventral (DV) axis of early Drosophila embryos, while repressors establish ventral boundaries. Yet recent studies have provided evidence that repressors act to specify the dorsal boundary of intermediate neuroblasts defective (ind), a gene expressed in a stripe along the DV axis in lateral regions of the embryo. Here we show that a short 12 base pair sequence (“the A-box”) present twice within the ind CRM is both necessary and sufficient to support transcriptional repression in dorsal regions of embryos. To identify binding factors, we conducted affinity chromatography using the A-box element and found a number of DNA-binding proteins and chromatin-associated factors using mass spectroscopy. Only Grainyhead (Grh), a CP2 transcription factor with a unique DNA-binding domain, was found to bind the A-box sequence. Our results suggest that Grh acts as an activator to support expression of ind, which was surprising as we identified this factor using an element that mediates dorsally-localized repression. Grh and Dorsal both contribute to ind transcriptional activation. However, another recent study found that the repressor Capicua (Cic) also binds to the A-box sequence. While Cic was not identified through our A-box affinity chromatography, utilization of the same site, the A-box, by both factors Grh (activator) and Cic (repressor) may also support a “switch-like” response that helps to sharpen the ind dorsal boundary. Furthermore, our results also demonstrate that TGF-β signaling acts to refine ind CRM expression in an A-box independent manner in dorsal-most regions, suggesting that tiers of repression act in dorsal regions of the embryo
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