59 research outputs found
In situ, broadband measurement of the radio frequency attenuation length at Summit Station, Greenland
Over the last 25 years, radiowave detection of neutrino-generated signals,
using cold polar ice as the neutrino target, has emerged as perhaps the most
promising technique for detection of extragalactic ultra-high energy neutrinos
(corresponding to neutrino energies in excess of 0.01 Joules, or
electron volts). During the summer of 2021 and in tandem with the initial
deployment of the Radio Neutrino Observatory in Greenland (RNO-G), we conducted
radioglaciological measurements at Summit Station, Greenland to refine our
understanding of the ice target. We report the result of one such measurement,
the radio-frequency electric field attenuation length . We find an
approximately linear dependence of on frequency with the best fit of
the average field attenuation for the upper 1500 m of ice: MHz m for
frequencies MHz.Comment: 13 pages, 8 figures, Accepted to Journal of Glaciolog
Precision measurement of the index of refraction of deep glacial ice at radio frequencies at Summit Station, Greenland
Glacial ice is used as a target material for the detection of ultra-high
energy neutrinos, by measuring the radio signals that are emitted when those
neutrinos interact in the ice. Thanks to the large attenuation length at radio
frequencies, these signals can be detected over distances of several
kilometers. One experiment taking advantage of this is the Radio Neutrino
Observatory Greenland (RNO-G), currently under construction at Summit Station,
near the apex of the Greenland ice sheet. These experiments require a thorough
understanding of the dielectric properties of ice at radio frequencies. Towards
this goal, calibration campaigns have been undertaken at Summit, during which
we recorded radio reflections off internal layers in the ice sheet. Using data
from the nearby GISP2 and GRIP ice cores, we show that these reflectors can be
associated with features in the ice conductivity profiles; we use this
connection to determine the index of refraction of the bulk ice as n=1.778 +/-
0.006
Search for low-mass dark matter via bremsstrahlung radiation and the Migdal effect in SuperCDMS
We present a new analysis of previously published SuperCDMS data using a profile likelihood framework to search for sub-GeV dark matter (DM) particles through two inelastic scattering channels: bremsstrahlung radiation and the Migdal effect. By considering these possible inelastic scattering channels, experimental sensitivity can be extended to DM masses that are undetectable through the DM-nucleon elastic scattering channel, given the energy threshold of current experiments. We exclude DM masses down to 220 MeV/c2 at 2.7×10−30 cm2 via the bremsstrahlung channel. The Migdal channel search provides overall considerably more stringent limits and excludes DM masses down to 30 MeV/c2 at 5.0×10−30 cm2
Antibody levels to the class I and II epitopes of the M protein and myosin are related to group A streptococcal exposure in endemic populations
Rheumatic fever (RF)/rheumatic heart disease (RHD) and post-streptococcal glomerulonephritis are thought to be autoimmune diseases, and follow group A streptococcal (GAS) infection. Different GAS M types have been associated with rheumatogenicity or nephritogenicity and categorized into either of two distinct classes (I or II) based on amino acid sequences present within the repeat region ('C' repeats) of the M protein. Sera from ARF patients have previously been shown to contain elevated levels of antibodies to the class I-specific epitope and myosin with the class I-specific antibodies also being cross-reactive to myosin, suggesting a disease association. This study shows that immunoreactivity of the class I-specific peptide and myosin does not differ between controls and acute RF (ARF)/RHD in populations that are highly endemic for GAS, raising the possibility that the association is related to GAS exposure, not the presence of ARF/RHD. Peptide inhibition studies suggest that the class I epitope may be conformational and residue 10 of the peptide is critical for antibody binding. We demonstrate that correlation of antibody levels between the class I and II epitope is due to class II-specific antibodies recognizing a common epitope with class I which is contained within the sequence RDL-ASRE. Our results suggest that antibody prevalence to class I and II epitopes and myosin is associated with GAS exposure, and that antibodies to these epitopes are not an indicator of disease nor a pathogenic factor in endemic populations
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