31 research outputs found
Lateral density distributions of muons and electrons in EAS from the KASCADE-Grande data for different zenith angle intervals
Features of Muon Arrival Time Distributions of High Energy EAS at Large Distances From the Shower Axis
In view of the current efforts to extend the KASCADE experiment
(KASCADE-Grande) for observations of Extensive Air Showers (EAS) of primary
energies up to 1 EeV, the features of muon arrival time distributions and their
correlations with other observable EAS quantities have been scrutinised on
basis of high-energy EAS, simulated with the Monte Carlo code CORSIKA and using
in general the QGSJET model as generator. Methodically various correlations of
adequately defined arrival time parameters with other EAS parameters have been
investigated by invoking non-parametric methods for the analysis of
multivariate distributions, studying the classification and misclassification
probabilities of various observable sets. It turns out that adding the arrival
time information and the multiplicity of muons spanning the observed time
distributions has distinct effects improving the mass discrimination. A further
outcome of the studies is the feature that for the considered ranges of primary
energies and of distances from the shower axis the discrimination power of
global arrival time distributions referring to the arrival time of the shower
core is only marginally enhanced as compared to local distributions referring
to the arrival of the locally first muon.Comment: 24 pages, Journal Physics G accepte
Implications of the cosmic ray spectrum for the mass composition at the highest energies
The significant attenuation of the cosmic-ray flux above eV
suggests that the observed high-energy spectrum is shaped by the so-called GZK
effect. This interaction of ultra-high-energy cosmic rays (UHECRs) with the
ambient radiation fields also affects their composition. We review the effect
of photo-dissociation interactions on different nuclear species and analyze the
phenomenology of secondary proton production as a function of energy. We show
that, by itself, the UHECR spectrum does not constrain the cosmic-ray
composition at their extragalactic sources. While the propagated composition
(i.e., as observed at Earth) cannot contain significant amounts of intermediate
mass nuclei (say between He and Si), whatever the source composition, and while
it is vastly proton-dominated when protons are able to reach energies above
eV at the source, we show that the propagated composition can be
dominated by Fe and sub-Fe nuclei at the highest energies, either if the
sources are very strongly enriched in Fe nuclei (a rather improbable
situation), or if the accelerated protons have a maximum energy of a few
eV at the sources. We also show that in the latter cases, the
expected flux above eV is very much reduced compared to the case
when protons dominate in this energy range, both at the sources and at Earth.Comment: 16 pages, 7 figure
Centaurus A: the one extragalactic source of cosmic rays with energies above the knee
The origin of cosmic rays at all energies is still uncertain. In this paper
we present and explore an astrophysical scenario to produce cosmic rays with
energy ranging from below o eV. We show here that
just our Galaxy and the radio galaxy Cen A, each with their own galactic cosmic
ray particles, but with those from the radio galaxy pushed up in energy by a
relativistic shock in the jet emanating from the active black hole, are
sufficient to describe the most recent data in the energy range PeV to near
ZeV. Data are available over this entire energy range from the experiments
KASCADE, KASCADE-Grande and Pierre Auger Observatory. The energy spectrum
calculated here correctly reproduces the measured spectrum beyond the knee, and
contrary to widely held expectations, no other extragalactic source population
is required to explain the data, even at energies far below the general cutoff
expected at eV, the Greisen-Zatsepin-Kuzmin turn-off due to
interaction with the cosmological microwave background. We present several
predictions for the source population, the cosmic ray composition and the
propagation to Earth which can be tested in the near future
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