52 research outputs found
Radio wavefront of very inclined extensive air-showers observed with extended and sparse radio arrays
In this article we perform a simulation-based study of the shape of the
electromagnetic wavefront of air showers induced by cosmic rays. We show that
for showers with zenith angles larger than 60{\deg}, a point-source like
description of the wave-front is sufficient and that the reconstructed position
of this point-source is a potential proxy for the determination of the nature
of the cosmic rays initiating the showers, with performances similar to those
obtained using the depth of shower maximum.Comment: 16 pages, 8 figures. arXiv admin note: text overlap with
arXiv:2107.0320
New results from H.E.S.S. observations of galaxy clusters
Clusters of galaxies are believed to contain a significant population of
cosmic rays. From the radio and probably hard X-ray bands it is known that
clusters are the spatially most extended emitters of non-thermal radiation in
the Universe. Due to their content of cosmic rays, galaxy clusters are also
potential sources of VHE (>100 GeV) gamma rays. Recently, the massive, nearby
cluster Abell 85 has been observed with the H.E.S.S. experiment in VHE gamma
rays with a very deep exposure as part of an ongoing campaign. No significant
gamma-ray signal has been found at the position of the cluster. The
non-detection of this object with H.E.S.S. constrains the total energy of
cosmic rays in this system. For a hard spectral index of the cosmic rays of
-2.1 and if the cosmic-ray energy density follows the large scale gas density
profile, the limit on the fraction of energy in these non-thermal particles
with respect to the total thermal energy of the intra-cluster medium is 8% for
this particular cluster. This value is at the lower bounds of model
predictions.Comment: 4 pages, one figure, invited talk at the 2nd Heidelberg workshop:
"High-Energy Gamma-rays and Neutrinos from Extra-Galactic Sources", January
13 - 16, 2009, to be published in Int. J. Mod. Phys.
Polarisation signatures in radio for inclined cosmic-ray induced air-shower identification
Autonomous radio-detection, i.e., detection of air-showers with standalone
radio arrays, is one of the major technical challenges to overcome for the next
generation astroparticle detectors. In this context, we study polarisation
signatures of simulated radio signals to perform an identification of the
associated air-showers initiated by cosmic-rays and neutrinos. We compare the
two sources of radio emission (the charge excess and geomagnetic) and show that
the former is almost negligible for inclined (zenith angle )
cosmic-ray air-showers. This provides an efficient background rejection
criterion at the DAQ level, based on the projection of the total electric field
along the direction of the local magnetic field. This relevant quantity can be
easily computed -- even in an online treatment -- for antennas measuring three
orthogonal polarisations. Independently of the experimental antenna layout, we
estimate that assuming a random polarisation of noise events, a rejection from
(for a non favorable detector location) to (for a
favorable location) of the noise induced events and a trigger efficiency of 87%
(93%) with a () trigger threshold level should be
achievable. We also show that neutrino-induced showers present a charge excess
to geomagnetic signal ratio up to times higher than for cosmic ray
showers. Although this characteristic makes the identification of
neutrino-induced showers challenging via the method developed here, it provides
an efficient criterion to perform an offline discrimination between cosmic-ray
and neutrino primaries. The stronger charge excess emission will also help the
reconstruction of air-shower parameters, such as the core position.Comment: 19 pages, 26 figures, 3 tables. Accepted in Astroparticle Physic
Exploring the Cosmic Reionization Epoch in Frequency Space: An Improved Approach to Remove the Foreground in 21 cm Tomography
Aiming to correctly restore the redshifted 21 cm signals emitted by the
neutral hydrogen during the cosmic reionization processes, we re-examine the
separation approaches based on the quadratic polynomial fitting technique in
frequency space to investigate whether they works satisfactorily with complex
foreground, by quantitatively evaluate the quality of restored 21 cm signals in
terms of sample statistics. We construct the foreground model to characterize
both spatial and spectral substructures of the real sky, and use it to simulate
the observed radio spectra. By comparing between different separation
approaches through statistical analysis of restored 21 cm spectra and
corresponding power spectra, as well as their constraints on the mean halo bias
and average ionization fraction of the reionization processes, at
and the noise level of 60 mK we find that, although the complex
foreground can be well approximated with quadratic polynomial expansion, a
significant part of Mpc-scale components of the 21 cm signals (75% for Mpc scales and 34% for Mpc scales) is lost because
it tends to be mis-identified as part of the foreground when
single-narrow-segment separation approach is applied. The best restoration of
the 21 cm signals and the tightest determination of and can be
obtained with the three-narrow-segment fitting technique as proposed in this
paper. Similar results can be obtained at other redshifts.Comment: 33 pages, 14 figures. Accepted for publication in Ap
Development of a radio-detection method array for the observation of ultra-high energy neutrino induced showers
The recent demonstration by the CODALEMA Collaboration of the ability of the
radio-detection technique for the characterization of UHE cosmic-rays calls for
the use of this powerful method for the observation of UHE neutrinos. For this
purpose, an adaptation of the existing 21CM Array (China) is presently under
achievment. In an exceptionally low electromagnetic noise level, 10160
log-periodic 50-200 MHz antennas sit along two high valleys, surrounded by
mountain chains. This lay-out results in 30-60 km effective rock thicnesses for
neutrino interactions with low incidence trajectories along the direction of
two 4-6 km baselines. We will present first in-situ radio measurements
demonstrating that this environment shows particularly favourable conditions
for the observation of electromagnetic decay signals of taus originating from
the interaction of 10^17-20 eV tau neutrinos.Comment: 4pages, 3 figures, Contribution to appear in the proceedings of ARENA
2008 conferenc
The Giant Radio Array for Neutrino Detection
High-energy neutrino astronomy will probe the working of the most violent phenomena in the Universe. The Giant Radio Array for Neutrino Detection (GRAND) project consists of an array of ∼ 105 radio antennas deployed over ∼ 200 000 km2 in a mountainous site. It aims at detecting high-energy neutrinos via the measurement of air showers induced by the decay in the atmosphere of τ leptons produced by the interaction of cosmic neutrinos under the Earth surface. Our objective with GRAND is to reach a neutrino sensitivity of 5 × 10−11E−2 GeV−1 cm−2 s−1 sr−1 above 3 × 1016 eV. This sensitivity ensures the detection of cosmogenic neutrinos in the most pessimistic source models, and up to 100 events per year are expected for the standard models. GRAND would also probe the neutrino signals produced at the potential sources of UHECRs
The GRAND project and GRANDProto300 experiment
The Giant Array for Neutrino Detection (GRAND) is a proposal for a giant observatory of ultra-high energy cosmic particles (neutrinos, cosmic rays and gamma rays). It will be composed of twenty subarrays of 10 000 antennas each, totaling a detection area of 200 000 km2. GRAND will reach unprecedented sensitivity to neutrinos allowing to detect cosmogenic neutrinos while its sub-degree angular resolution will also make it possible to hunt for point sources and possibly start neutrino astronomy. Combined with its gigantic exposure to ultra-high energy cosmic rays and gamma rays, GRAND will be a powerful tool to solve the century-long mistery of the nature and origin of the particles with highest energy in the Universe. On the path to GRAND, the GRANDProto300 experiment will be deployed in 2020 over a total area of 200 km2. It primarly aims at validating the detection concept of GRAND, but also proposes a rich science program centered on a precise and complete measurement of the air showers initiated by cosmic rays with energies between 1016.5 and 1018 eV, a range where we expect to observe the transition between the Galactic and extra-galactic origin of cosmic rays
The Giant Radio Array for Neutrino Detection
International audienceThe Giant Radio Array for Neutrino Detection (GRAND) is a proposal for a giant observatory of ultra-high energy cosmic particles (neutrinos, cosmic rays and gamma rays). It will be composed of twenty subarrays of 10 000 antennas each, to be deployed after 2030 at various locations around the world, totaling a detection area of 200 000 km². According to simulations, GRAND will reach unprecedented sensitivity to neutrinos of astrophysical origin with energies above 10^17 eV, sufficient to guarantee their detection. GRAND sub-degree angular resolution will also make it possible to hunt for point sources and possibly start neutrino astronomy. This, combined with the large instantaneous field of view expected from the location of the sub-arrays in different continents and hemispheres, will make GRAND a key instrument in the forth-coming era of multi-messenger transient astronomy, during which the century-long mystery of the nature and origin of the particles with highest energy in the Universe may be solved
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