302 research outputs found
Comparison of Hadronic Interaction Models at Auger Energies
The three hadronic interaction models DPMJET 2.55, QGSJET 01, and SIBYLL 2.1,
implemented in the air shower simulation program CORSIKA, are compared in the
energy range of interest for the Pierre Auger experiment. The model dependence
of relevant quantities in individual hadronic interactions and air showers is
investigated.Comment: Contribution to XII Int. Symp. on Very High Energy Cosmic Ray
Interactions, 4 pages, 8 figure
The background from single electromagnetic subcascades for a stereo system of air Cherenkov telescopes
The MAGIC experiment, a very large Imaging Air Cherenkov Telescope (IACT)
with sensitivity to low energy (E < 100 GeV) VHE gamma rays, has been operated
since 2004. It has been found that the gamma/hadron separation in IACTs becomes
much more difficult below 100 GeV [Albert et al 2008] A system of two large
telescopes may eventually be triggered by hadronic events containing Cherenkov
light from only one electromagnetic subcascade or two gamma subcascades, which
are products of the single pi^0 decay. This is a possible reason for the
deterioration of the experiment's sensitivity below 100 GeV. In this paper a
system of two MAGIC telescopes working in stereoscopic mode is studied using
Monte Carlo simulations. The detected images have similar shapes to that of
primary gamma-rays and they have small sizes (mainly below 400 photoelectrons
(p.e.)) which correspond to an energy of primary gamma-rays below 100 GeV. The
background from single or two electromagnetic subcascdes is concentrated at
energies below 200 GeV. Finally the number of background events is compared to
the number of VHE gamma-ray excess events from the Crab Nebula. The
investigated background survives simple cuts for sizes below 250 p.e. and thus
the experiment's sensitivity deteriorates at lower energies.Comment: 15 pages, 7 figures, published in Journ.of Phys.
Impact of Uncertainties in Hadron Production on Air-Shower Predictions
At high energy, cosmic rays can only be studied by measuring the extensive
air showers they produce in the atmosphere of the Earth. Although the main
features of air showers can be understood within a simple model of successive
interactions, detailed simulations and a realistic description of particle
production are needed to calculate observables relevant to air shower
experiments. Currently hadronic interaction models are the main source of
uncertainty of such simulations. We will study the effect of using different
hadronic models available in CORSIKA and CONEX on extensive air shower
predictions.Comment: 12 pages, 6 figures, to appear in the proceedings of International
Conference on Interconnection between High Energy Physics and Astroparticle
Physics: From Colliders to Cosmic Rays, Prague, Czech Republic, 7-13 Sep 200
Charm Production in DPMJET
In this work, charm production in the {\sc dpmjet} hadronic jet simulation is
compared to experimental data. Since the major application of {\sc dpmjet} is
the simulation of cosmic ray-induced air showers, the version of the code
integrated in the CORSIKA simulation package has been used for the comparison.
Wherever necessary, adjustments have been made to improve agreement between
simulation and data. With the availability of new muon/neutrino detectors that
combine a large fiducial volume with large amounts of shielding, investigation
of prompt muons and neutrinos from cosmic ray interactions will be feasible for
the first time. Furthermore, above TeV charmed particle decay
becomes the dominant background for diffuse extraterrestrial neutrino flux
searches. A reliable method to simulate charm production in high-energy
proton-nucleon interactions is therefore required.Comment: 10 pages, to be published in JCA
Natural limit on the gamma/hadron separation for a stand alone air Cherenkov telescope
The gamma/hadron separation in the imaging air Cherenkov telescope technique
is based on differences between images of a hadronic shower and a gamma induced
electromagnetic cascade. One may expect for a large telescope that a detection
of hadronic events containing Cherenkov light from one gamma subcascade only is
possible. In fact, simulations show that for the MAGIC telescope their fraction
in the total protonic background is about 1.5% to 5.2% depending on the trigger
threshold. It has been found that such images have small sizes (mainly below
400 photoelectrons) which correspond to the low energy primary gamma's (below
100 GeV). It is shown that parameters describing shapes of images from one
subcascade have similar distributions to primary gamma events, so those
parameters are not efficient in all methods of gamma selection. Similar studies
based on MC simulations are presented also for the images from 2 gamma
subcascades which are products of the same pi^0 decay. The ratio of the number
of the expected background from false gamma and one pi^0 to the number of the
triggered high energy photons from the Crab direction has been estimated for
images with a small alpha parameter to show that the occurrence of this type of
protonic shower is the reason for the difficulties with true gamma selection at
low energies.Comment: 12 pages, 7 figures, published in Journal of Physics
Limits to the energy resolution of a single Air Cherenkov Telescope at low energies
The photon density on the ground is a fundamental quantity in all experiments
based on Cherenkov light measurements, e.g. in the Imaging Air Cherenkov
Telescopes (IACT). IACT's are commonly and successfully used in order to search
and study Very High Energy (VHE) gamma-ray sources. Difficulties with
separating primary photons from primary hadrons (mostly protons) in Cherenkov
experiments become larger at lower energies. I have calculated longitudinal and
lateral density distributions and their fluctuations at low energies basing on
Monte Carlo simulations (for vertical gamma cascades and protonic showers) to
check the influence of the detector parameters on the possible measurement.
Relative density fluctuations are significantly higher in proton than in photon
induced showers. Taking into account the limited detector field of view (FOV)
implies the changes of these calculated distributions for both types of primary
particles and causes an enlargement in relative fluctuations. Absorption due to
Rayleigh and Mie scattering has an impact on mean values but does not change
relative fluctuations. The total number of Cherenkov photons is more sensitive
to the observation height in gamma cascades than in proton showers at low
primary energies. The relative fluctuations of the density do not depend on the
reflector size in the investigated size range (from 240 m^2 up to 960 m^2).
This implies that a single telescope with a mirror area larger than that of the
MAGIC telescope cannot achieve better energy resolution than estimated and
presented in this paper. The correlations between longitudinal and lateral
distributions are much more pronounced for primary gamma-ray than for primary
proton showers.Comment: 21 pages, 11 figures, accepted for publication in Journal of Physics
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
On inconsistency of experimental data on primary nuclei spectra with sea level muon intensity measurements
For the first time a complete set of the most recent direct data on primary
cosmic ray spectra is used as input into calculations of muon flux at sea level
in wide energy range GeV. Computations have been performed
with the CORSIKA/QGSJET and CORSIKA/VENUS codes. The comparison of the obtained
muon intensity with the data of muon experiments shows, that measurements of
primary nuclei spectra conform to sea level muon data only up to several tens
of GeV and result in essential deficit of muons at higher energies. As it
follows from our examination, uncertainties in muon flux measurements and in
the description of nuclear cascades development are not suitable to explain
this contradiction, and the only remaining factor, leading to this situation,
is underestimation of primary light nuclei fluxes. We have considered
systematic effects, that may distort the results of the primary cosmic ray
measurements with the application of the emulsion chambers. We suggest, that
re-examination of these measurements is required with the employment of
different hadronic interaction models. Also, in our point of view, it is
necessary to perform estimates of possible influence of the fact, that sizable
fraction of events, identified as protons, actually are antiprotons. Study of
these cosmic ray component begins to attract much attention, but today nothing
definite is known for the energies GeV. In any case, to realize whether
the mentioned, or some other reasons are the sources of disagreement of the
data on primaries with the data on muons, the indicated effects should be
thoroughly analyzed
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
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