15,387 research outputs found
Atmospheric Charged Ratio and Measurement of Muon Annual Modulation with a Liquid Scintillation Detector at Soudan
We report a measurement of muon annual modulation in a 12-liter liquid
scintillation detector with a live-time of more than 4 years at the Soudan
Underground Laboratory. Muon minimum ionization in the detector is identified
by its observed pulse shape and large energy deposition. The measured muon rate
in the detector is 28.692.09 muons per day with a modulation amplitude of
2.66 1.0\% and a phase at Jul 22 36.2 days. This annual modulation
is correlated with the variation of the effective atmospheric temperature in
the stratosphere. The correlation coefficient, , is determined to
be . This can be interpreted as a measurement of the
atmospheric charged kaon to pion (/) ratio of 0.094
for 7 TeV, consistent with the measurement from the MINOS far
detector. To further constrain the value of / ratio, a Geant4
simulation of the primary cosmic-ray protons with energy up to 100 TeV is
implemented to study the correlation of / ratio and the muon annual
modulation for muon energy greater than 0.5 TeV. We find out that a charged
/ ratio of 0.1598, greater than the upper bound (0.138) from this work
at the production point 30 km above the Earth surface in the stratosphere
cannot induce muon annual modulation at the depth of Soudan.Comment: 6 pages and 11 figure
Early Results on Radioactive Background Characterization for Sanford Laboratory and DUSEL Experiments
Measuring external sources of background for a deep underground laboratory at
the Homestake Mine is an important step for the planned low-background
experiments. The naturally occurring -ray fluxes at different levels in
the Homestake Mine are studied using NaI detectors and Monte Carlo simulations.
A simple algorithm is developed to convert the measured -ray rates into
-ray fluxes. A good agreement between the measured and simulated
-ray fluxes is achieved with the knowledge of the chemical composition
and radioactivity levels in the rock. The neutron fluxes and -ray
fluxes are predicted by Monte Carlo simulations for different levels including
inaccessible levels that are under construction for the planned low background
experiments.Comment: 16 pages, 2 figures, and 9 table
Scaling Theory of Heat Transport in Quasi-1D Disordered Harmonic Chains
We introduce a variant of the Banded Random Matrix ensemble and show, using
detailed numerical analysis and theoretical arguments, that the phonon heat
current in disordered quasi-one-dimensional lattices obeys a one-parameter
scaling law. The resulting beta-function indicates that an anomalous Fourier
law is applicable in the diffusive regime, while in the localization regime the
heat current decays exponentially with the sample size. Our approach opens a
new way to investigate the effects of Anderson localization in heat conduction,
based on the powerful ideas of scaling theory.Comment: Supplemental Report on calculation of heat current include
Periodicities in the occurrence of aurora as indicators of solar variability
A compilation of records of the aurora observed in China from the Time of the Legends (2000 - 3000 B.C.) to the mid-18th century has been used to infer the frequencies and strengths of solar activity prior to modern times. A merging of this analysis with auroral and solar activity patterns during the last 200 years provides basically continuous information about solar activity during the last 2000 years. The results show periodicities in solar activity that contain average components with a long period (approx. 412 years), three middle periods (approx. 38 years, approx. 77 years, and approx. 130 years), and the well known short period (approx. 11 years)
Ground States for Exponential Random Graphs
We propose a perturbative method to estimate the normalization constant in
exponential random graph models as the weighting parameters approach infinity.
As an application, we give evidence of discontinuity in natural parametrization
along the critical directions of the edge-triangle model.Comment: 12 pages, 3 figures, 1 tabl
Probing Localization in Absorbing Systems via Loschmidt Echos
We measure Anderson localization in quasi-one-dimensional waveguides in the
presence of absorption by analyzing the echo dynamics due to small
perturbations. We specifically show that the inverse participation number of
localized modes dictates the decay of the Loschmidt echo, differing from the
Gaussian decay expected for diffusive or chaotic systems. Our theory, based on
a random matrix modeling, agrees perfectly with scattering echo measurements on
a quasi one-dimensional microwave cavity filled with randomly distributed
scatterers.Comment: cross-reference with nonlin.CD-Chaotic Dynamic
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