8,559 research outputs found
Research Program towards Observation of Neutrino-Nucleus Coherent Scattering
The article describes the research program pursued by the TEXONO
Collaboration towards an experiment to observe coherent scattering between
neutrinos and the nucleus at the power reactor. The motivations of studying
this process are surveyed. In particular, a threshold of 100-200 eV has been
achieved with an ultra-low-energy germanium detector prototype. This detection
capability at low energy can also be adapted to conduct searches of Cold Dark
Matter in the low-mass region as well as to enhance the sensitivities in the
study of neutrino magnetic moments.Comment: 5 pages, 8 figures ; Proceedings of TAUP-2005 Workshop, Spain, 2005.
Updated on 2006/9/15 for Proceedings of Neutrino-2006 Conference, Santa Fe,
200
Individual alpha power predicts language comprehension
Alpha power attenuation during cognitive task performing has been suggested to reflect a process of release of inhibition, increase of excitability, and thereby benefit the improvement of performance. Here, we hypothesized that changes in individual alpha power during the execution of a complex language comprehension task may correlate with the individual performance in that task. We tested this using magnetoencephalography (MEG) recorded during comprehension of German sentences of different syntactic complexity. Results showed that neither the frequency nor the power of the spontaneous oscillatory activity at rest were associated with the individual performance. However, during the execution of a sentences processing task, the individual alpha power attenuation did correlate with individual language comprehension performance. Source reconstruction localized effects in temporal-parietal regions of both hemispheres. While the effect of increased task difficulty is localized in the right hemisphere, the difference in power attenuation between tasks of different complexity exhibiting a correlation with performance was localized in left temporal-parietal brain regions known to be associated with language processing. From our results, we conclude that in-task attenuation of individual alpha power is related to the essential mechanisms of the underlying cognitive processes, rather than merely to general phenomena like attention or vigilance
Alpha power during task performance predicts individual language comprehension
Alpha power attenuation during cognitive task performing has been suggested to reflect a process of release of inhibition, increase of excitability, and thereby benefit the improvement of performance. Here, we hypothesized that changes in individual alpha power during the execution of a complex language comprehension task may correlate with the individual performance in that task. We tested this using magnetoencephalography (MEG) recorded during comprehension of German sentences of different syntactic complexity. Results showed that neither the frequency nor the power of the spontaneous oscillatory activity at rest were associated with the individual performance. However, during the execution of a sentences processing task, the individual alpha power attenuation did correlate with individual language comprehension performance. Source reconstruction localized effects in temporal-parietal regions of both hemispheres. While the effect of increased task difficulty is localized in both hemispheres, the difference in power attenuation between tasks of different complexity exhibiting a correlation with performance was localized in left temporal-parietal brain regions known to be associated with language processing. Our results support the notion that in-task attenuation of individual alpha power is related to the essential mechanisms of the underlying cognitive processes, rather than merely to general phenomena like attention or vigilance
Constraints on Non-Commutative Physics Scale with Neutrino-Electron Scattering
Neutrino-electron scatterings () are purely leptonic processes with
robust Standard Model (SM) predictions. Their measurements can therefore
provide constraints to physics beyond SM. Non-commutative (NC) field theories
modify space-time commutation relations, and allow neutrino electromagnetic
couplings at the tree level. Their contribution to neutrino-electron scattering
cross-section was derived. Constraints were placed on the NC scale parameter
from experiments with reactor and accelerator
neutrinos. The most stringent limit of at 95%
confidence level improves over the direct bounds from collider experiments.Comment: 6 pages, 2 figures, 2 tables, V2: minor revisions to match published
versio
Production of Electron Neutrinos at Nuclear Power Reactors and the Prospects for Neutrino Physics
High flux of electron neutrinos(\nue) is produced at nuclear power reactors
through the decays of nuclei activated by neutron capture. Realistic simulation
studies on the neutron transport and capture at the reactor core were
performed. The production of \chr51 and \fe55 give rise to mono-energetic
\nue's at Q-values of 753 keV and 231 keV and fluxes of
and \nue/fission, respectively. Using data from a
germanium detector at the Kuo-Sheng Power Plant, we derived direct limits on
the \nue magnetic moment and the radiative lifetime of \mu_{\nu} < 1.3
\times 10^{-8} ~ \mub and at 90%
confidence level (CL), respectively. Indirect bounds on were also inferred. The \nue-flux can be enhanced by loading
selected isotopes to the reactor core, and the potential applications and
achievable statistical accuracies were examined. These include accurate
cross-section measurements, studies of mixing angle and
monitoring of plutonium production.Comment: 5 pages, 3 figures, 7 table
Limits on Light Weakly Interacting Massive Particles from the First 102.8 kg day Data of the CDEX-10 Experiment
We report the first results of a light weakly interacting massive particles
(WIMPs) search from the CDEX-10 experiment with a 10 kg germanium detector
array immersed in liquid nitrogen at the China Jinping Underground Laboratory
with a physics data size of 102.8 kg day. At an analysis threshold of 160 eVee,
improved limits of 8 and 3 cm at a
90\% confidence level on spin-independent and spin-dependent WIMP-nucleon cross
sections, respectively, at a WIMP mass () of 5 GeV/ are
achieved. The lower reach of is extended to 2 GeV/.Comment: 5 pages, 4 figure
Global axisymmetric stability analysis for a composite system of two gravitationally coupled scale-free discs
In a composite system of gravitationally coupled stellar and gaseous discs,
we perform linear stability analysis for axisymmetric coplanar perturbations
using the two-fluid formalism. The background stellar and gaseous discs are
taken to be scale-free with all physical variables varying as powers of
cylindrical radius with compatible exponents. The unstable modes set in as
neutral modes or stationary perturbation configurations with angular frequency
.Comment: 7 pages using AAS styl
Search for Light Weakly-Interacting-Massive-Particle Dark Matter by Annual Modulation Analysis with a Point-Contact Germanium Detector at the China Jinping Underground Laboratory
We present results on light weakly interacting massive particle (WIMP)
searches with annual modulation (AM) analysis on data from a 1-kg mass -type
point-contact germanium detector of the CDEX-1B experiment at the China Jinping
Underground Laboratory. Datasets with a total live time of 3.2 yr within a 4.2
yr span are analyzed with analysis threshold of 250 eVee. Limits on
WIMP-nucleus (-) spin-independent cross sections as function of WIMP
mass () at 90\% confidence level (C.L.) are derived using the dark
matter halo model. Within the context of the standard halo model, the 90\% C.L.
allowed regions implied by the DAMA/LIBRA and CoGeNT AM-based analysis are
excluded at 99.99\% and 98\% C.L., respectively. These results correspond to
the best sensitivity at 6 among WIMP AM
measurements to date.Comment: 5 pages, 4 figure
Prospects of cold dark matter searches with an ultra-low-energy germanium detector
The report describes the research program on the development of
ultra-low-energy germanium detectors, with emphasis on WIMP dark matter
searches. A threshold of 100 eV is achieved with a 20 g detector array,
providing a unique probe to the low-mas WIMP. Present data at a surface
laboratory is expected to give rise to comparable sensitivities with the
existing limits at the WIMP-mass range. The projected
parameter space to be probed with a full-scale, kilogram mass-range experiment
is presented. Such a detector would also allow the studies of neutrino-nucleus
coherent scattering and neutrino magnetic moments.Comment: 3 pages, 4 figures, Proceedings of TAUP-2007 Conferenc
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