LOPES, the LOFAR prototype station, was an antenna array for cosmic-ray air showers operating from 2003 to 2013 within the KASCADE-Grande experiment. Meanwhile, the analysis is finished and the data ...of air-shower events measured by LOPES are available with open access in the KASCADE Cosmic Ray Data Center (KCDC). This article intends to provide a summary of the achievements, results, and lessons learned from LOPES. By digital, interferometric beamforming the detection of air showers became possible in the radio-loud environment of the Karlsruhe Institute of Technology (KIT). As a prototype experiment, LOPES tested several antenna types, array configurations and calibration techniques, and pioneered analysis methods for the reconstruction of the most important shower parameters, i.e., the arrival direction, the energy, and mass-dependent observables such as the position of the shower maximum. In addition to a review and update of previously published results, we also present new results based on end-to-end simulations including all known instrumental properties. For this, we applied the detector response to radio signals simulated with the CoREAS extension of CORSIKA, and analyzed them in the same way as measured data. Thus, we were able to study the detector performance more accurately than before, including some previously inaccessible features such as the impact of noise on the interferometric cross-correlation beam. These results led to several improvements, which are documented in this paper and can provide useful input for the design of future cosmic-ray experiments based on the digital radio-detection technique.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We report the observation of a steepening in the cosmic ray energy spectrum of heavy primary particles at about 8×10(16) eV. This structure is also seen in the all-particle energy spectrum, but is ...less significant. Whereas the "knee" of the cosmic ray spectrum at 3-5×10(15) eV was assigned to light primary masses by the KASCADE experiment, the new structure found by the KASCADE-Grande experiment is caused by heavy primaries. The result is obtained by independent measurements of the charged particle and muon components of the secondary particles of extensive air showers in the primary energy range of 10(16) to 10(18) eV. The data are analyzed on a single-event basis taking into account also the correlation of the two observables.
KASCADE and KASCADE-Grande were multi-detector installations to measure individual air showers of cosmic rays at ultra-high energy. Based on data sets measured by KASCADE and KASCADE-Grande, 90% C.L. ...upper limits to the flux of gamma-rays in the primary cosmic ray flux are determined in an energy range of eV. The analysis is performed by selecting air showers with a low muon content as expected for gamma-ray-induced showers compared to air showers induced by energetic nuclei. The best upper limit of the fraction of gamma-rays to the total cosmic ray flux is obtained at eV with . Translated to an absolute gamma-ray flux this sets constraints on some fundamental astrophysical models, such as the distance of sources for at least one of the IceCube neutrino excess models.
The ‘KASCADE Cosmic ray Data Centre’ is a web portal (
https://kcdc.ikp.kit.edu
), where the data of the astroparticle physics experiment KASCADE-Grande are made available for the interested public. ...The KASCADE experiment was a large-area detector for the measurement of high-energy cosmic rays via the detection of extensive air showers. The multi-detector installations KASCADE and its extension KASCADE-Grande stopped the active data acquisition in 2013 after more than 20 years of data taking. In several updates since our first release in 2013 with KCDC we provide the public measured and reconstructed parameters of more than 433 million air showers. In addition, KCDC provides meta data information and documentation to enable a user outside the community of experts to perform their own data analysis. Simulation data from three different high energy interaction models have been made available as well as a compilation of measured and published spectra from various experiments. In addition, detailed educational examples shall encourage high-school students and early stage researchers to learn about astroparticle physics, cosmic radiation as well as the handling of Big Data and about the sustainable and public provision of scientific data.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We report on a dark matter search for a Weakly Interacting Massive Particle (WIMP) in the mass range
m
χ
∈
4
,
30
GeV
/
c
2
with the EDELWEISS-III experiment. A 2D profile likelihood analysis is ...performed on data from eight selected detectors with the lowest energy thresholds leading to a combined fiducial exposure of 496 kg-days. External backgrounds from
γ
- and
β
-radiation, recoils from
206
Pb
and neutrons as well as detector intrinsic backgrounds were modelled from data outside the region of interest and constrained in the analysis. The basic data selection and most of the background models are the same as those used in a previously published analysis based on boosted decision trees (BDT)
1
. For the likelihood approach applied in the analysis presented here, a larger signal efficiency and a subtraction of the expected background lead to a higher sensitivity, especially for the lowest WIMP masses probed. No statistically significant signal was found and upper limits on the spin-independent WIMP-nucleon scattering cross section can be set with a hypothesis test based on the profile likelihood test statistics. The 90 % C.L. exclusion limit set for WIMPs with
m
χ
=
4
GeV
/
c
2
is
1.6
×
10
-
39
cm
2
, which is an improvement of a factor of seven with respect to the BDT-based analysis. For WIMP masses above
15
GeV
/
c
2
the exclusion limits found with both analyses are in good agreement.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The radio technique is a promising method for detection of cosmic-ray air showers of energies around 100PeV and higher with an array of radio antennas. Since the amplitude of the radio signal can be ...measured absolutely and increases with the shower energy, radio measurements can be used to determine the air-shower energy on an absolute scale. We show that calibrated measurements of radio detectors operated in coincidence with host experiments measuring air showers based on other techniques can be used for comparing the energy scales of these host experiments. Using two approaches, first via direct amplitude measurements, and second via comparison of measurements with air shower simulations, we compare the energy scales of the air-shower experiments Tunka-133 and KASCADE-Grande, using their radio extensions, Tunka-Rex and LOPES, respectively. Due to the consistent amplitude calibration for Tunka-Rex and LOPES achieved by using the same reference source, this comparison reaches an accuracy of approximately 10% – limited by some shortcomings of LOPES, which was a prototype experiment for the digital radio technique for air showers. In particular we show that the energy scales of cosmic-ray measurements by the independently calibrated experiments KASCADE-Grande and Tunka-133 are consistent with each other on this level.
We present the results of the search for large-scale anisotropies in the arrival directions of cosmic rays performed with the KASCADE-Grande experiment at energies higher than eV. To eliminate ...spurious anisotropies due to atmospheric or instrumental effects we apply the east-west method. We show, using the solar time distribution of the number of counts, that this technique allow us to remove correctly the count variations not associated to real anisotropies. By applying the east-west method we obtain the distribution of number of counts in intervals of 20 minutes of sidereal time. This distribution is then analyzed by searching for a dipole component; the significance of the amplitude of the first harmonic is 3.5 , therefore, we derive its upper limit. The phase of the first harmonic is determined with an error of a few hours and is in agreement with the measurements obtained in the 1014 < E < 2 × 1015 eV energy range by the EAS-TOP, IceCube, and IceTop experiments. This supports the hypothesis of a change of the phase of the first harmonic at energies greater than ∼2 × 1014 eV.
We present the results of a search for elastic scattering from galactic dark matter in the form of Weakly Interacting Massive Particles (WIMPs) in the 4-30 GeV/$c^2$ mass range. We make use of a 582 ...kg-day fiducial exposure from an array of 800 g Germanium bolometers equipped with a set of interleaved electrodes with full surface coverage. We searched specifically for $\sim 2.5-20$ keV nuclear recoils inside the detector fiducial volume. As an illustration the number of observed events in the search for 5 (resp. 20) GeV/$c^2$ WIMPs are 9 (resp. 4), compared to an expected background of 6.1 (resp. 1.4). A 90% CL limit of $4.3\times 10^{-40}$ cm$^2$ (resp. $9.4\times 10^{-44}$ cm$^2$) is set on the spin-independent WIMP-nucleon scattering cross-section for 5 (resp. 20) GeV/$c^2$ WIMPs. This result represents a 41-fold improvement with respect to the previous EDELWEISS-II low-mass WIMP search for 7 GeV/$c^2$ WIMPs. The derived constraint is in tension with hints of WIMP signals from some recent experiments, thus confirming results obtained with different detection techniques.
We report the first direct measurement of the overall characteristics of microwave radio emission from extensive air showers. Using a trigger provided by the KASCADE-Grande air shower array, the ...signals of the microwave antennas of the Cosmic-Ray Observation via Microwave Emission experiment have been read out and searched for signatures of radio emission by high-energy air showers in the GHz frequency range. Microwave signals have been detected for more than 30 showers with energies above 3×10^{16} eV. The observations presented in this Letter are consistent with a mainly forward-directed and polarized emission process in the GHz frequency range. The measurements show that microwave radiation offers a new means of studying air showers at E≥10^{17} eV.
The nature of ultrahigh-energy cosmic rays (UHECRs) at energies >1020 eV remains a mystery. They are likely to be of extragalactic origin, but should be absorbed within ∼50 Mpc through interactions ...with the cosmic microwave background. As there are no sufficiently powerful accelerators within this distance from the Galaxy, explanations for UHECRs range from unusual astrophysical sources to exotic string physics. Also unclear is whether UHECRs consist of protons, heavy nuclei, neutrinos or γ-rays. To resolve these questions, larger detectors with higher duty cycles and which combine multiple detection techniques are needed. Radio emission from UHECRs, on the other hand, is unaffected by attenuation, has a high duty cycle, gives calorimetric measurements and provides high directional accuracy. Here we report the detection of radio flashes from cosmic-ray air showers using low-cost digital radio receivers. We show that the radiation can be understood in terms of the geosynchrotron effect. Our results show that it should be possible to determine the nature and composition of UHECRs with combined radio and particle detectors, and to detect the ultrahigh-energy neutrinos expected from flavour mixing.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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