38 research outputs found
On the possibilities of large-scale radio and fiber optics detectors in cosmic rays
Different variants of radio and fiber optics detectors for registration of super high energy cascades in the atmosphere and in dense media are discussed. Particularly the possibilities for investigation of quasi horizontal cosmic ray showers (CRS) and simulated muons from these CRS with the help of radio detectors and fiber optics detectors located on the ice surface are considered
Experimental Limit on the Cosmic Diffuse Ultra-high Energy Neutrino Flux
We report results from 120 hours of livetime with the Goldstone Lunar
Ultra-high energy neutrino Experiment (GLUE). The experiment searches for <10
ns microwave pulses from the lunar regolith, appearing in coincidence at two
large radio telescopes separated by 22 km and linked by optical fiber. Such
pulses would arise from subsurface electromagnetic cascades induced by
interactions of >= 100 EeV neutrinos in the lunar regolith. No candidates are
yet seen, and the implied limits constrain several current models for
ultra-high energy neutrino fluxes.Comment: 4 pages, 4 figures, revtex4 style. New intro section, Fig. 2, Fig 4;
in final PRL revie
Characterization of neutrino signals with radiopulses in dense media through the LPM effect
We discuss the possibilities of detecting radio pulses from high energy
showers in ice, such as those produced by PeV and EeV neutrino interactions. It
is shown that the rich radiation pattern structure in the 100 MHz to few GHz
allows the separation of electromagnetic showers induced by photons or
electrons above 100 PeV from those induced by hadrons. This opens up the
possibility of measuring the energy fraction transmitted to the electron in a
charged current electron neutrino interaction with adequate sampling of the
angular distribution of the signal. The radio technique has the potential to
complement conventional high energy neutrino detectors with flavor information.Comment: 5 pages, 4 ps figures. Submitted to Phys. Rev. Let
Observation of the Askaryan Effect: Coherent Microwave Cherenkov Emission from Charge Asymmetry in High Energy Particle Cascades
We present the first direct experimental evidence for the charge excess in
high energy particle showers predicted nearly 40 years ago by Askaryan. We
directed bremsstrahlung photons from picosecond pulses of 28.5 GeV electrons at
the SLAC Final Focus Test Beam facility into a 3.5 ton silica sand target,
producing electromagnetic showers several meters long. A series of antennas
spanning 0.3 to 6 GHz were used to detect strong, sub-nanosecond radio
frequency pulses produced whenever a shower was present. The measured electric
field strengths are consistent with a completely coherent radiation process.
The pulses show 100% linear polarization, consistent with the expectations of
Cherenkov radiation. The field strength versus depth closely follows the
expected particle number density profile of the cascade, consistent with
emission from excess charge distributed along the shower. These measurements
therefore provide strong support for experiments designed to detect high energy
cosmic rays and neutrinos via coherent radio emission from their cascades.Comment: 10 pages, 4 figures. Submitted to Phys. Rev. Let
Neuregulin-1β, Biomarkers of Inflammation and Myocardial Fibrosis in Heart Failure Patients
Neuregulin-1β (NRG-1) is an emerging biomarker of heart failure (HF). The mechanisms of its action in HF patients are yet to be investigated. Cardioprotective and anti-inflammatory effects of NRG-1 have been reported.Aim. To assess NRG-1 levels in HF patients and investigate the association between NRG-1 and biomarkers of inflammation and myocardial fibrosis.Material and Methods. NRG-1, biomarkers of inflammation and fibrosis (hsCRP, IL-6, sVCAM-1, MMP-9, Galectin-3, ST2, TGF-β) were assessed in 47 patients with HF and preserved ejection fraction (HFpEF); 39 patients with HF and reduced ejection (HFrEF) and 40 healthy participants. The associations between NRG-1 and biomarkers of inflammation and fibrosis, as well as the composite outcomes of cardiovascular death and HF hospitalisations were assessed.Results. Median NRG-1 levels in HFpEF were 0.969 (0.348; 1.932) ng/ml, in HFrEF – 0.63 (0.348; 1.932), in healthy participants 0.379 (0.195; 0.861) ng/ml, and was significantly higher in HFpEF compared to healthy volunteers (р=0.004). There was no difference in NRG-1 concentration between HFpEF and HFrEF. In HF patients, all biomarkers of inflammation and fibrosis were higher than in controls. ST2, IL-6 and TGF-β were significantly higher in HFrEF compared to HFpEF patients, while hsCRP, sVCAM-1, MMP-9, and Galectin-3 levels were comparable. In HFpEF, NRG-1 was associated with hsCRP (rs=0.378, p=0.023) and IL-6 (rs=0.378, p=0.014). Median follow-up time in patients with HFpEF and in patients was 312 (236; 388) days, in HFrEF – 147 (98; 237) days. In HFpEF, 2 patients died and 19 were hospitalized due to HF. In HFrEF, 10 deaths and 19 hospitalizations were registered. Kaplan-Mayer analysis showed that HFpEF patients with increased NRG-1 and IL-6 had higher levels of HF hospitalisation (log rank test, р=0.046 and р=0.012, respectively). In a multivariable cox proportional hazard model, the association between the NRG-1 and outcomes remained significant after adjustment for age, gender and NTproBNP but diminished when hsCRP and IL-6 were included in the model.Conclusion. NGR-1 level significantly higher in HFpEF compared to healthy participants, and comparable with NRG-1 concentrations in HFrEF. In HFpEF, NRG-1 was associated with biomarkers of inflammation and fibrosis. The prognostic value of NRG-1 in HF requires further investigations
Observations of the Askaryan Effect in Ice
We report on the first observations of the Askaryan effect in ice: coherent
impulsive radio Cherenkov radiation from the charge asymmetry in an
electromagnetic (EM) shower. Such radiation has been observed in silica sand
and rock salt, but this is the first direct observation from an EM shower in
ice. These measurements are important since the majority of experiments to date
that rely on the effect for ultra-high energy neutrino detection are being
performed using ice as the target medium. As part of the complete validation
process for the Antarctic Impulsive Transient Antenna (ANITA) experiment, we
performed an experiment at the Stanford Linear Accelerator Center (SLAC) in
June 2006 using a 7.5 metric ton ice target, yielding results fully consistent
with theoretical expectations.Comment: 4 pages, 5 figures, minor correction
Accelerator Measurements of the Askaryan effect in Rock Salt: A Roadmap Toward Teraton Underground Neutrino Detectors
We report on further SLAC measurements of the Askaryan effect: coherent radio
emission from charge asymmetry in electromagnetic cascades. We used synthetic
rock salt as the dielectric medium, with cascades produced by GeV
bremsstrahlung photons at the Final Focus Test Beam. We extend our prior
discovery measurements to a wider range of parameter space and explore the
effect in a dielectric medium of great potential interest to large scale
ultra-high energy neutrino detectors: rock salt (halite), which occurs
naturally in high purity formations containing in many cases hundreds of cubic
km of water-equivalent mass. We observed strong coherent pulsed radio emission
over a frequency band from 0.2-15 GHz. A grid of embedded dual-polarization
antennas was used to confirm the high degree of linear polarization and track
the change of direction of the electric-field vector with azimuth around the
shower. Coherence was observed over 4 orders of magnitude of shower energy. The
frequency dependence of the radiation was tested over two orders of magnitude
of UHF and microwave frequencies. We have also made the first observations of
coherent transition radiation from the Askaryan charge excess, and the result
agrees well with theoretical predictions. Based on these results we have
performed a detailed and conservative simulation of a realistic GZK neutrino
telescope array within a salt-dome, and we find it capable of detecting 10 or
more contained events per year from even the most conservative GZK neutrino
models.Comment: 15 pages, 16 figures, submitted to Phys. Rev.