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R. Engel

Publications and source records attributed to R. Engel.

At least 307 records · Page 17Linked to original sources
arXiv2010

Sensitivity of KASCADE-Grande data to hadronic interaction models

KASCADE-Grande is a large detector array dedicated for studies of high-energy cosmic rays in the primary energy range from 100 TeV to 1 EeV. The multi-detector concept of the experimental set-up offers the possibility to measure simultaneously various observables related to the electromagnetic, muonic, and hadronic air shower components. The experimental data are compared to predictions of CORSIKA simulations using high-energy hadronic interaction models (e.g. QGSJET or EPOS), as well as low-energy interaction models (e.g. FLUKA or GHEISHA). This contribution will summarize the results of such investigations. In particular, the validity of the new EPOS version 1.99 for EAS with energy around 100 PeV will be discussed.

astro-ph.HE↗
arXiv2010

The KASCADE-Grande experiment: measurements of the all-particle energy spectrum of cosmic rays

The all-particle energy spectrum as measured by the KASCADE-Grande experiment for E = 10^{16} - 10^{18} eV is presented within the framework of the QGSJET II/FLUKA hadronic interaction models. Three different methods were applied based on the muon size and the total number of charged particles individually and in combination. From the study it is found that the spectrum cannot be completely described by a smooth power law due to the presence of characteristic features.

astro-ph.HE↗
arXiv2010

On noise treatment in radio measurements of cosmic ray air showers

Precise measurements of the radio emission by cosmic ray air showers require an adequate treatment of noise. Unlike to usual experiments in particle physics, where noise always adds to the signal, radio noise can in principle decrease or increase the signal if it interferes by chance destructively or constructively. Consequently, noise cannot simply be subtracted from the signal, and its influence on amplitude and time measurement of radio pulses must be studied with care. First, noise has to be determined consistently with the definition of the radio signal which typically is the maximum field strength of the radio pulse. Second, the average impact of noise on radio pulse measurements at individual antennas is studied for LOPES. It is shown that a correct treatment of noise is especially important at low signal-to-noise ratios: noise can be the dominant source of uncertainty for pulse height and time measurements, and it can systematically flatten the slope of lateral distributions. The presented method can also be transfered to other experiments in radio and acoustic detection of cosmic rays and neutrinos.

astro-ph.IM↗
arXiv2009

Lateral Distribution of the Radio Signal in Extensive Air Showers Measured with LOPES

The antenna array LOPES is set up at the location of the KASCADE-Grande extensive air shower experiment in Karlsruhe, Germany and aims to measure and investigate radio pulses from Extensive Air Showers. The coincident measurements allow us to reconstruct the electric field strength at observation level in dependence of general EAS parameters. In the present work, the lateral distribution of the radio signal in air showers is studied in detail. It is found that the lateral distributions of the electric field strengths in individual EAS can be described by an exponential function. For about 20% of the events a flattening towards the shower axis is observed, preferentially for showers with large inclination angle. The estimated scale parameters R0 describing the slope of the lateral profiles range between 100 and 200 m. No evidence for a direct correlation of R0 with shower parameters like azimuth angle, geomagnetic angle, or primary energy can be found. This indicates that the lateral profile is an intrinsic property of the radio emission during the shower development which makes the radio detection technique suitable for large scale applications.

astro-ph.HE↗
arXiv2009

Influence of Low Energy Hadronic Interactions on Air-shower Simulations

Experiments measuring cosmic rays above an energy of 10^14 eV deduce the energy and mass of the primary cosmic ray particles from air-shower simulations. We investigate the importance of hadronic interactions at low and high energies on the distributions of muons and electrons in showers on ground. In air shower simulation programs, hadronic interactions below an energy threshold in the range from 80 GeV to 500 GeV are simulated by low energy interaction models, like Fluka or Gheisha, and above that energy by high energy interaction models, e.g. Sibyll or QGJSJet. We find that the impact on shower development obtained by switching the transition energy from 80 GeV to 500 GeV is comparable to the difference obtained by switching between Fluka and Gheisha.

astro-ph.CO↗
arXiv2009

Cosmic Rays from the Knee to the Highest Energies

This review summarizes recent developments in the understanding of high-energy cosmic rays. It focuses on galactic and presumably extragalactic particles in the energy range from the knee (10^15 eV) up to the highest energies observed (>10^20 eV). Emphasis is put on observational results, their interpretation, and the global picture of cosmic rays that has emerged during the last decade.

astro-ph.HE↗
arXiv2009

Universality of electron-positron distributions in extensive air showers

Using a large set of simulated extensive air showers, we investigate universality features of electron and positron distributions in very-high-energy cosmic-ray air showers. Most particle distributions depend only on the depth of the shower maximum and the number of particles in the cascade at this depth. We provide multi-dimensional parameterizations for the electron-positron distributions in terms of particle energy, vertical and horizontal momentum angle, lateral distance, and time distribution of the shower front. These parameterizations can be used to obtain realistic electron-positron distributions in extensive air showers for data analysis and simulations of Cherenkov radiation, fluorescence signal, and radio emission.

astro-ph.HE↗
arXiv2008

Active Galactic Nuclei: Sources for ultra high energy cosmic rays?

The origin of ultra high energy cosmic rays promises to lead us to a deeper understanding of the structure of matter. This is possible through the study of particle collisions at center-of-mass energies in interactions far larger than anything possible with the Large Hadron Collider, albeit at the substantial cost of no control over the sources and interaction sites. For the extreme energies we have to identify and understand the sources first, before trying to use them as physics laboratories. Here we describe the current stage of this exploration. The most promising contenders as sources are radio galaxies and gamma ray bursts. The sky distribution of observed events yields a hint favoring radio galaxies. Key in this quest are the intergalactic and galactic magnetic fields, whose strength and structure are not yet fully understood. Current data and statistics do not yet allow a final judgment. We outline how we may progress in the near future.

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arXiv2008

Dependence of geosynchrotron radio emission on the energy and depth of maximum of cosmic ray showers

Based on CORSIKA and REAS2 simulations, we investigate the dependence of geosynchrotron radio emission from extensive air showers on the energy of the primary cosmic ray and the depth of the shower maximum. It is found that at a characteristic lateral distance, the amplitude of the bandpass-filtered radio signal is directly proportional to the energy deposited in the atmosphere by the electromagnetic cascade, with an RMS uncertainty due to shower-to-shower fluctuations of less than 3%. In addition, the ratio of this radio amplitude and that at a larger lateral distance is directly related to the atmospheric depth of the shower maximum, with an RMS uncertainty of ~15-20 g cm-2. By measuring these quantities, geosynchrotron radio emission from cosmic ray air showers can be used to infer the energy of the primary particle and the depth of the air shower maximum on a shower-to-shower basis.

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arXiv2008

Altitude dependence of fluorescence light emission by extensive air showers

Fluorescence light is induced by extensive air showers while developing in the Earth's atmosphere. The number of emitted fluorescence photons depends on the conditions of the air and on the energy deposited by the shower particles at every stage of the development. In a previous model calculation, the pressure and temperature dependences of the fluorescence yield have been studied on the basis of kinetic gas theory, assuming temperature-independent molecular collision cross-sections. In this work we investigate the importance of temperature-dependent collision cross-sections and of water vapour quenching on the expected fluorescence yield. The calculations will be applied to simulated air showers while using actual atmospheric profiles to estimate the influence on the reconstructed energy of extensive air showers.

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arXiv2008

Applying Shower Development Universality to KASCADE Data

On basis of the theorem of a universal shower development stating that a hadronically generated extensive air shower is completely described by the primary energy, the position of the shower maximum and a parameter related to the total muon number, the so-called correlation curve method is developed and applied to KASCADE data. Correlation information of the muon and electron content of showers measured by the KASCADE experiment are used for the reconstruction of energy and mass of primary cosmic rays. Systematic uncertainties of the method and the results are discussed in detail. It is shown that by this method general tendencies in spectrum and composition indeed can be revealed, but the absolute normalization in energy and mass scale requires much more detailed simulations.

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arXiv2008

Latest Results from the Air Shower Simulation Programs CORSIKA and CONEX

Interpretation of EAS measurements strongly depends on detailed air shower simulations. The uncertainty in the prediction of shower observables for different primary particles and energies is currently dominated by differences between hadronic interaction models. The new models QGSJETII-3 and EPOS 1.6, which reproduce all major results of existing accelerator data (including detailed data of RHIC experiments for EPOS), have been implemented in the air shower simulation programs CORSIKA and CONEX. We show predictions of these new models and compare them with those from older models such as QGSJET01 or SIBYLL. Results for important air shower observables are discussed in detail.

astro-ph↗
arXiv2008

Reconstruction of Longitudinal Profiles of Ultra-High Energy Cosmic Ray Showers from Fluorescence and Cherenkov Light Measurements

We present a new method for the reconstruction of the longitudinal profile of extensive air showers induced by ultra-high energy cosmic rays. In contrast to the typically considered shower size profile, this method employs directly the ionization energy deposit of the shower particles in the atmosphere. Due to universality of the energy spectra of electrons and positrons, both fluorescence and Cherenkov light can be used simultaneously as signal to infer the shower profile from the detected light. The method is based on an analytic least-square solution for the estimation of the shower profile from the observed light signal. Furthermore, the extrapolation of the observed part of the profile with a Gaisser-Hillas function is discussed and the total statistical uncertainty of shower parameters like total energy and shower maximum is calculated.

astro-ph↗
arXiv2007

Energy and composition sensitivity of geosynchrotron radio emission from EAS

We analyse the sensitivity of geosynchrotron radio emission from inclined extensive air showers to the energy and mass of primary cosmic rays. We demonstrate that radio emission measurements at suitable lateral distances can infer both the number of electrons and positrons in the shower maximum and the atmospheric depth of the maximum on a shower-to-shower basis. Alternatively, measurements at a fixed lateral distance but in two different observing frequency bands yield comparable information. An RMS error of 5% in the determination of the number of electrons and positrons at shower maximum can be achieved. Through the determination of these quantities, geosynchrotron radiation provides access to the energy and mass of primary cosmic rays on a shower-to-shower basis.

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