1,652 research outputs found
Third Level Trigger for the Fluorescence Telescopes of the Pierre Auger Observatory
The trigger system for the Auger fluorescence telescopes is implemented in
hard- and software for an efficient selection of fluorescence light tracks
induced by high-energy extensive air showers. The algorithm of the third stage
uses the multiplicity signal of the hardware for fast rejection of lightning
events with above 99% efficiency. In a second step direct muon hits in the
camera and random triggers are rejected by analyzing the space-time correlation
of the pixels. The trigger algorithm was tested with measured and simulated
showers and implemented in the electronics of the fluorescence telescopes. A
comparison to a prototype trigger without multiplicity shows the superiority of
this approach, e.g. the false rejection rate is a factor 10 lower.Comment: 8 pages, 7 figures, to be published in NIM A; 1 typo correcte
Search for hidden-photon dark matter with the FUNK experiment
Many extensions of the Standard Model of particle physics predict a parallel
sector of a new U(1) symmetry, giving rise to hidden photons. These hidden
photons are candidate particles for cold dark matter. They are expected to
kinetically mix with regular photons, which leads to a tiny oscillating
electric-field component accompanying dark matter particles. A conducting
surface can convert such dark matter particles into photons which are emitted
almost perpendicularly to the surface. The corresponding photon frequency
follows from the mass of the hidden photons. In this contribution we present a
preliminary result on a hidden photon search in the visible and near-UV
wavelength range that was done with a large, 14 m2 spherical metallic mirror
and discuss future dark matter searches in the eV and sub-eV range by
application of different detectors for electromagnetic radiation.Comment: Contribution to the 35th International Cosmic Ray Conference
ICRC2017, 10 to 20 July, 2017, Bexco, Busan, Korea. arXiv admin note: text
overlap with arXiv:1711.0296
Machine learning for automatic prediction of the quality of electrophysiological recordings
The quality of electrophysiological recordings varies a lot due to technical and biological variability and neuroscientists inevitably have to select âgoodâ recordings for further analyses. This procedure is time-consuming and prone to selection biases. Here, we investigate replacing human decisions by a machine learning approach. We define 16 features, such as spike height and width, select the most informative ones using a wrapper method and train a classifier to reproduce the judgement of one of our expert electrophysiologists. Generalisation performance is then assessed on unseen data, classified by the same or by another expert. We observe that the learning machine can be equally, if not more, consistent in its judgements as individual experts amongst each other. Best performance is achieved for a limited number of informative features; the optimal feature set being different from one data set to another. With 80â90% of correct judgements, the performance of the system is very promising within the data sets of each expert but judgments are less reliable when it is used across sets of recordings from different experts. We conclude that the proposed approach is relevant to the selection of electrophysiological recordings, provided parameters are adjusted to different types of experiments and to individual experimenters
First results of the air shower experiment KASCADE
The main goals of the KASCADE (KArlsruhe Shower Core and Array DEtector)
experiment are the determination of the energy spectrum and elemental
composition of the charged cosmic rays in the energy range around the knee at
ca. 5 PeV. Due to the large number of measured observables per single shower a
variety of different approaches are applied to the data, preferably on an
event-by-event basis. First results are presented and the influence of the
high-energy interaction models underlying the analyses is discussed.Comment: 3 pages, 3 figures included, to appear in the TAUP 99 Proceedings,
Nucl. Phys. B (Proc. Suppl.), ed. by M. Froissart, J. Dumarchez and D.
Vignau
Large scale cosmic-ray anisotropy with KASCADE
The results of an analysis of the large scale anisotropy of cosmic rays in
the PeV range are presented. The Rayleigh formalism is applied to the right
ascension distribution of extensive air showers measured by the KASCADE
experiment.The data set contains about 10^8 extensive air showers in the energy
range from 0.7 to 6 PeV. No hints for anisotropy are visible in the right
ascension distributions in this energy range. This accounts for all showers as
well as for subsets containing showers induced by predominantly light
respectively heavy primary particles. Upper flux limits for Rayleigh amplitudes
are determined to be between 10^-3 at 0.7 PeV and 10^-2 at 6 PeV primary
energy.Comment: accepted by The Astrophysical Journa
Electron, Muon, and Hadron Lateral Distributions Measured in Air-Showers by the KASCADE Experiment
Measurements of electron, muon, and hadron lateral distributions of extensive
air showers as recorded by the KASCADE experiment are presented. The data cover
the energy range from about 5x10^14 eV up to almost 10^17 eV and extend from
the inner core region to distances of 200 m. The electron and muon
distributions are corrected for mutual contaminations by taking into account
the detector properties in the experiment. All distributions are well described
by NKG-functions. The scale radii describing the electron and hadron data best
are approx. 30 m and 10 m, respectively. We discuss the correlation between
scale radii and `age' parameter as well as their dependence on shower size,
zenith angle, and particle energy threshold.Comment: 28 pages, 14 figures, Accepted for publication in Astroparticle
Physic
Primary Proton Spectrum of Cosmic Rays measured with Single Hadrons
The flux of cosmic-ray induced single hadrons near sea level has been
measured with the large hadron calorimeter of the KASCADE experiment. The
measurement corroborates former results obtained with detectors of smaller size
if the enlarged veto of the 304 m^2 calorimeter surface is encounted for. The
program CORSIKA/QGSJET is used to compute the cosmic-ray flux above the
atmosphere. Between E_0=300 GeV and 1 PeV the primary proton spectrum can be
described with a power law parametrized as
dJ/dE_0=(0.15+-0.03)*E_0^{-2.78+-0.03} m^-2 s^-1 sr^-1 TeV^-1. In the TeV
region the proton flux compares well with the results from recent measurements
of direct experiments.Comment: 13 pages, accepted by Astrophysical Journa
KASCADE-Grande Limits on the Isotropic Diffuse Gamma-Ray Flux between 100 TeV and 1 EeV
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.Comment: Published in The Astrophysical Journal, Volume 848, Number 1. Posted
on: October 5, 201
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