8,795 research outputs found
Atmospheric effects on extensive air showers observed with the Surface Detector of the Pierre Auger Observatory
Atmospheric parameters, such as pressure (P), temperature (T) and density,
affect the development of extensive air showers initiated by energetic cosmic
rays. We have studied the impact of atmospheric variations on extensive air
showers by means of the surface detector of the Pierre Auger Observatory. The
rate of events shows a ~10% seasonal modulation and ~2% diurnal one. We find
that the observed behaviour is explained by a model including the effects
associated with the variations of pressure and density. The former affects the
longitudinal development of air showers while the latter influences the Moliere
radius and hence the lateral distribution of the shower particles. The model is
validated with full simulations of extensive air showers using atmospheric
profiles measured at the site of the Pierre Auger Observatory.Comment: 24 pages, 9 figures, accepted for publication in Astroparticle
Physic
Simulations of black hole air showers in cosmic ray detectors
We present a comprehensive study of TeV black hole events in Earth's
atmosphere originated by cosmic rays of very high energy. An advanced fortran
Monte Carlo code is developed and used to simulate black hole extensive air
showers from ultrahigh-energy neutrino-nucleon interactions. We investigate the
characteristics of these events, compare the black hole air showers to standard
model air showers, and test different theoretical and phenomenological models
of black hole formation and evolution. The main features of black hole air
showers are found to be independent of the model considered. No significant
differences between models are likely to be observed at fluorescence telescopes
and/or ground arrays. We also discuss the tau ``double bang'' signature in
black hole air showers. We find that the energy deposited in the second bang is
too small to produce a detectable peak. Our results show that the theory of
TeV-scale black holes in ultrahigh-energy cosmic rays leads to robust
predictions, but the fine prints of new physics are hardly to be investigated
through atmospheric black hole events in the near future.Comment: 18 pages, 9 figure
Report on Tests and Measurements of Hadronic Interaction Properties with Air Showers
We present a summary of recent tests and measurements of hadronic interaction
properties with air showers. This report has a special focus on muon density
measurements. Several experiments reported deviations between simulated and
recorded muon densities in extensive air showers, while others reported no
discrepancies. We combine data from eight leading air shower experiments to
cover shower energies from PeV to tens of EeV. Data are combined using the
z-scale, a unified reference scale based on simulated air showers.
Energy-scales of experiments are cross-calibrated. Above 10 PeV, we find a muon
deficit in simulated air showers for each of the six considered hadronic
interaction models. The deficit is increasing with shower energy. For the
models EPOS-LHC and QGSJet-II.04, the slope is found significant at 8 sigma.Comment: Submitted to the Proceedings of UHECR201
Air-Shower Spectroscopy at horizons
Horizontal and Upward air-showers are suppressed by deep atmosphere opacity
and by the Earth shadows. In such noise-free horizontal and upward directions
rare Ultra High Cosmic rays and rarer neutrino induced air-showers may shine,
mostly mediated by resonant PeVs interactions in air or by higher energy Tau
Air-showers originated by neutrino tau skimming the Earth. At high altitude
(mountains, planes, balloons) the air density is so rarefied that nearly all
common air-showers might be observed at their maximal growth at a tuned
altitude and directions. The arrival angle samples different distances and the
corresponding most probable primary cosmic ray energy. The larger and larger
distances (between observer and C.R. interaction) make wider and wider the
shower area and it enlarge the probability to be observed (up to three order of
magnitude more than vertical showers); the observation of a maximal
electromagnetic shower development may amplify the signal by two-three order of
magnitude (respect suppressed shower at sea level); the peculiar altitude-angle
range may disentangle at best the primary cosmic ray energy and composition.
Even from existing mountain observatory the up-going air-showers may trace,
above the horizons, PeV-EeV high energy cosmic rays and, below the horizons,
PeV-EeV neutrino astronomy: their early signals may be captured in already
existing gamma telescopes as Magic at Canarie, while facing the Earth edges
during (useless) cloudy nights.Comment: 9 pages, 9 figures, submitted to Prog. Part. Nucl. Phy
Arrival directions of large air showers, low-mu showers and old-age low-mu air showers observed at St. Chacaltaya
Arrival directions of air showers with primary energies in the range 10 to the 16.5 power eV to 10 to the 18th power eV show the first harmonic in right ascension (RA) with amplitude of 2.7 + or - 1.0% and phase of 13-16h. However, the second harmonic in RA slightly seen for showers in the range 10 to the 18th power eV to 10 to the 19th power eV disappeared by accumulation of observed showers. The distribution of arrival directions of low-mu air showers with primary energies around 10 to the 15th power eV observed at Chacaltaya from 1962 to 1967 is referred to, relating to the above-mentioned first harmonic. Also presented in this paper are arrival directions of old-age low-mu air showers observed at Chacaltaya from 1962 to 1967, for recent interest in gamma-ray air showers
Polarized radio emission from extensive air showers measured with LOFAR
We present LOFAR measurements of radio emission from extensive air showers.
We find that this emission is strongly polarized, with a median degree of
polarization of nearly , and that the angle between the polarization
direction of the electric field and the Lorentz force acting on the particles,
depends on the observer location in the shower plane. This can be understood as
a superposition of the radially polarized charge-excess emission mechanism,
first proposed by Askaryan and the geomagnetic emission mechanism proposed by
Kahn and Lerche. We calculate the relative strengths of both contributions, as
quantified by the charge-excess fraction, for individual air showers. We
find that the measured charge-excess fraction is higher for air showers
arriving from closer to the zenith. Furthermore, the measured charge-excess
fraction also increases with increasing observer distance from the air shower
symmetry axis. The measured values range from for very
inclined air showers at to for almost
vertical showers at . Both dependencies are in qualitative
agreement with theoretical predictions.Comment: 22 pages, 14 figures, accepted for publication in JCA
First Experimental Characterization of Microwave Emission from Cosmic Ray Air Showers
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 CROME (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 polarised
emission process in the GHz frequency range. The measurements show that
microwave radiation offers a new means of studying air showers at energies
above 10^17 eV.Comment: Accepted for publication in PR
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