117048840
Muon Flux Simulation and Comparison with Frejus Measurements
13891869
Rejection of the hypothesis that Mkn-501 TeV photons are pure Bose – Einstein condensates
The TeV energy spectrum of the Blazar type galaxy Mkn-501 as measured by the HEGRA air Cherenkov telescopes extends beyond 16 TeV and constitutes the most energetic photons observed from an extragalactic object. A fraction of the emitted spectrum is possibly absorbed in interactions with low energy photons of the diffuse extragalactic infrared radiation, which in turn offers the unique possibility to measure the diffuse infrared radiation density by exact TeV spectroscopy. The upper limit on the density of the extragalactic infrared radiation derived from the TeV observations imposes constraints on models of galaxy formation and stellar evolution. One of the recently published ideas to reduce the absorption of TeV photons is based upon the assumption Max-Planck-Institut für Kernphysik, Postfach 103980, D-69029 Heidelberg, Germany Max-Planck-Institut für Physik, Föhringer Ring 6, D-80805 München, Germany Universidad Complutense, Facultad de Ciencias F́isicas, Ciudad Universitaria, E-28040 Madrid, Spain Universität Hamburg, II. Institut für Experimentalphysik, Luruper Chaussee 149, D-22761 Hamburg, Germany Universität Kiel, Institut für Experimentelle und Angewandte Physik, Leibnizstraße 15-19, D-24118 Kiel, Germany Universität Wuppertal, Fachbereich Physik, Gaußstr.20, D-42097 Wuppertal, Germany Yerevan Physics Institute, Alikhanian Br. 2, 375036 Yerevan, Armenia On leave from Altai State University, Dimitrov Street 66, 656099 Barnaul, Russia Corresponding author: Dieter Horns Dieter.Horns@desy.de
197518521
A Search for gamma-ray emission from the galactic plane in the longitude range between 37 degrees and 43 degrees
117705808
Observations at large zenith angles
Cherenkov telescope observations at zenith angles >70° are capable of providing large collection areas for high energy γ-induced air showers. In order to provide a full Monte Carlo simulation of the large zenith angle observations the air shower simulation code CORSIKA was modified to treat particles in a curved geometry. First results of studies with the stand alone telescope HEGRA CT1 are presented.
123482754
Cherenkov light based measurement of extensive air showers around the knee with the HEGRA experiment
Data of the wide angle atmospheric Cherenkov light detector array AIROBICC and the scintillator matrix of the HEGRA air shower detector complex are combined to determine the energy spectrum and coarse composition of charged cosmic rays in the energy interval from 300 TeV to 10 PeV.
17460419
Energy spectrum and chemical composition of cosmic rays between 0.3 and 10 PeV determined from the Cherenkov-light and charged-particle distributions in air showers
Measurements of the lateral distribution of Cherenkov photons with the wide-angle atmospheric Cherenkov light detector array AIROBICC and of the charged particle lateral distribution with the scintillator matrix of the HEGRA air-shower detector complex in air showers are reported. They are used in conjunction to determine the energy spectrum and coarse chemical composition of charged cosmic rays in the energy interval from 0.3 PeV to 10 PeV. With the atmospheric shower-front sampling technique these detectors measure the electromagnetic component of an extensive air shower via the lateral density distribution of the shower particles and of the Cherenkov photons. The data are compared with events generated with the CORSIKA program package with the QGSJET hadronic-event generator. Consistency checks performed with primary energy-reconstruction methods based on different shower observables indicate satisfactory agreement between these extensive air shower simulations and the experimental data. This permits to derive results concerning the energy spectrum and composition of charged cosmic rays. The energy spectrum features a so called "knee" at
122960102
Search for point-like sources of ultra-high energy neutrinos at the Pierre Auger observatory and improved limit on the diffuse flux of tau neutrinos
The surface detector array of the Pierre Auger Observatory can detect neutrinos with energy E_ν between 10^17 eV and 10^20 eV from point-like sources across the sky south of +55 degrees and north of -65 degrees declinations. A search has been performed for highly inclined extensive air showers produced by the interaction of neutrinos of all flavors in the atmosphere (downward-going neutrinos), and by the decay of tau leptons originating from tau neutrino interactions in Earth's crust (Earth-skimming neutrinos). No candidate neutrinos have been found in data up to 2010 May 31. This corresponds to an equivalent exposure of ∼3.5 years of a full surface detector array for the Earth-skimming channel and ∼2 years for the downward-going channel. An improved upper limit on the diffuse flux of tau neutrinos has been derived. Upper limits on the neutrino flux from point-like sources have been derived as a function of the source declination. Assuming a differential neutrino flux k_PS . E_nu^-2. from a point-like source, 90% confidence level upper limits for k_PS at the level of ≈5x10^-7 and 2.5x10^-6 GeV cm^-2 s^-1 have been obtained over a broad range of declinations from the searches for Earth-skimming and downward-going neutrinos, respectively.
62829720
The measurement of the cosmic ray primary energy spectrum at 1016–1018 eV with the KASCADE-Grande experiment
The KASCADE-Grande experiment operates at Karlsruhe Institute of Technology (KIT) in Germany. Itʼs aim is the study of the primary cosmic radiation, through Extensive Air Shower detection, in the range 10 16 –10 18 eV. Here, measurements are of main interest to understand the high energy evolution of cosmic radiation: a change in the slope of the heavy primary spectrum is expected (as measured at lower energies for lighter primaries) as a possible confirmation of the predicted astrophysical mechanisms; moreover, in this range the transition from galactic to extragalactic radiation is supposed to take place and the observations could clarify the features of this transition, putting the basis for the interpretation of the data at the highest energies. For these tasks KASCADE-Grande fulfills very well the requirements, both concerning the acceptance and the experimental performances. The experiment is constituted by two co-operating arrays of detectors: the KASCADE array, with its 252 detectors in a dense grid of 200×200 m 2 and the Grande array, made of 37 detectors arranged on a wider area of 700×700 m 2 . The Grande array samples the total charged particles size of the air shower, while the KASCADE array provides the muon size In this contribution, KASCADE-Grande measurement of the cosmic ray primary energy spectrum is presented. The exploited technique, calibrated with simulations, combines the charged particles component and muon component on a shower by shower basis, performing the energy estimation of each primary event. Other techniques are also performed, for a better evaluation of systematics and a check of consistency of the hadronic interaction model used in simulations.
850959
Probing the radio emission from air showers with polarization measurements
The emission of radio waves from air showers has been attributed to the so-called geomagnetic emission process. At frequencies around 50 MHz this process leads to coherent radiation which can be observed with rather simple setups. The direction of the electric field induced by this emission process depends only on the local magnetic field vector and on the incoming direction of the air shower. We report on measurements of the electric field vector where, in addition to this geomagnetic component, another component has been observed that cannot be described by the geomagnetic emission process. The data provide strong evidence that the other electric field component is polarized radially with respect to the shower axis, in agreement with predictions made by Askaryan who described radio emission from particle showers due to a negative charge excess in the front of the shower. Our results are compared to calculations which include the radiation mechanism induced by this charge-excess process.
34250413
The spectrum of high-energy cosmic rays measured with KASCADE-Grande
Abstract The energy spectrum of cosmic rays between 10 16  eV and 10 18  eV, derived from measurements of the shower size (total number of charged particles) and the total muon number of extensive air showers by the KASCADE-Grande experiment, is described. The resulting all-particle energy spectrum exhibits strong hints for a hardening of the spectrum at approximately 2 · 10 16  eV and a significant steepening at ≈8 · 10 16  eV. These observations challenge the view that the spectrum is a single power law between knee and ankle. Possible scenarios generating such features are discussed in terms of astrophysical processes that may explain the transition region from galactic to extragalactic origin of cosmic rays.