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R. Engel

Publications and source records attributed to R. Engel.

At least 343 records · Page 19Linked to original sources
arXiv2005

Lateral width of shower image in the Auger fluorescence detector

The impact of the lateral distribution of light in extensive air showers on the detection and reconstruction of shower profiles is investigated for the Auger fluorescence telescopes. Based on three-dimensional simulations, the capability of the Auger telescopes to measure the lateral distribution of light is evaluated. The ability to infer the actual lateral distribution is confirmed by the comparison of detailed simulations with real data. The contribution of pixels located far from the axis of the shower image is calculated and the accepted signal is rescaled in order to reconstruct a correct shower profile. The analysis presented here shows that: (a) the Auger telescopes are able to observe the lateral distribution of showers and (b) the energy corrections to account for the signal in outlying pixels can exceed 10%, depending on shower geometry.

astro-ph↗
arXiv2005

Upper limit on the photon fraction in highest-energy cosmic rays from AGASA data

A new method to derive an upper limit on photon primaries from small data sets of air showers is developed which accounts for shower properties varying with the primary energy and arrival direction. Applying this method to the highest-energy showers recorded by the AGASA experiment, an upper limit on the photon fraction of 51% (67%) at a confidence level of 90% (95%) for primary energies above 1.25 * 10^20 eV is set. This new limit on the photon fraction above the GZK cutoff energy constrains the Z-burst model of the origin of highest-energy cosmic rays.

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arXiv2005

Atmospheric Profiles at the Southern Pierre Auger Observatory and their Relevance to Air Shower Measurement

The dependence of atmospheric conditions on altitude and time have to be known at the site of an air shower experiment for accurate reconstruction of extensive air showers and their simulations. The height-profile of atmospheric depth is of particular interest as it enters directly into the reconstruction of longitudinal shower development and of the primary energy and mass of cosmic rays. For the southern part of the Auger Observatory, the atmosphere has been investigated in a number of campaigns with meteorological radio soundings and with continuous measurements of ground-based weather stations. Focussing on atmospheric depth and temperature profiles, temporal variations are described and monthly profiles are developed. Uncertainties of the monthly atmospheres that are currently applied in the Auger reconstruction are discussed.

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arXiv2005

Impact of a new Cherenkov light parameterisation on the reconstruction of shower profiles from Auger hybrid data

The light signal measured by fluorescence telescopes receives - strongly depending on the shower geometry with respect to the detector - a non-negligible contribution from additionally produced Cherenkov light. This Cherenkov contribution has to be accounted for to determine primary parameters properly. In comparison to the previous ansatz used by other experiments, the impact of a new analytical description of Cherenkov light production in EAS on the Auger event reconstruction is investigated.

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arXiv2005

Hadronic multiparticle production in extensive air showers and accelerator experiments

Using CORSIKA for simulating extensive air showers, we study the relation between the shower characteristics and features of hadronic multiparticle production at low energies. We report about investigations of typical energies and phase space regions of secondary particles which are important for muon production in extensive air showers. Possibilities to measure relevant quantities of hadron production in existing and planned accelerator experiments are discussed.

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arXiv2005

Universal lateral distribution of energy deposit in air showers and its application to shower reconstruction

The light intensity distribution in a shower image and its implications to the primary energy reconstructed by the fluorescence technique are studied. Based on detailed CORSIKA energy deposit simulations, a universal analytical formula is derived for the lateral distribution of light in the shower image and a correction factor is obtained to account for the fraction of shower light falling into outlying pixels in the detector. The expected light profiles and the corresponding correction of the primary shower energy are illustrated for several typical event geometries. This correction of the shower energy can exceed 10%, depending on shower geometry.

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arXiv2004

First Results of Fast One-dimensional Hybrid Simulation of EAS Using CONEX

A hybrid simulation code is developed that is suited for fast one-dimensional simulations of shower profiles, including fluctuations. It combines the Monte Carlo simulation of high energy interactions with a fast numerical solution of cascade equations for the resulting distributions of secondary particles. Results obtained with this new code, called CONEX, are presented and compared to CORSIKA predictions.

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arXiv2004

On a possible photon origin of the most-energetic AGASA events

In this work the ultra high energy cosmic ray events recorded by the AGASA experiment are analysed. With detailed simulations of the extensive air showers initiated by photons, the probabilities are determined of the photonic origin of the 6 AGASA events for which the muon densities were measured and the reconstructed energies exceeded 10^20 eV. On this basis a new, preliminary upper limit on the photon fraction in cosmic rays above 10^20 eV is derived and compared to the predictions of exemplary top-down cosmic-ray origin models.

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arXiv2004

On the primary particle type of the most energetic Fly's Eye event

The longitudinal profile of the 320 EeV event observed by the Fly's Eye experiment is analysed. A method of testing the hypothesis of a specific primary particle type is described. Results for different particle types are summarized. For hadronic primaries between proton and iron nuclei, the discrepancy between observed and simulated profiles is in the range of 0.6-1.0 sigma for two different hadronic interaction models investigated. For primary photons, the discrepancy is 1.5sigma assuming a standard extrapolation of the photonuclear cross-section with energy. Larger values of the cross-section at highest energies make primary photon showers more similar to hadron-initiated events. The influence of varying the extrapolation of the photonuclear cross-section is studied.

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arXiv2004

d-Au and p-p collisions at RHIC and the multichain Monte Carlo Dpmjet-III

In this paper we compare systematically the two-component Dual Parton Model (DPM) event generator Dpmjet-III to d-Au and p-p data from RHIC. In this process we are able to improve the model. The need for fusion of chains and a recalibration of the model to obtain collision scaling in h-A and d-A collisions was found already in previous comparisons. Here, comparing to transverse momentum distributions of identified charged hadrons we find also the need to modify the transverse momentum distributions in the decay of hadronic strings, the basic building blocks of the model on soft hadronic collisions.

hep-ph↗
arXiv2004

Impact of Varying Atmospheric Profiles on Extensive Air Shower Observation: - Atmospheric Density and Primary Mass Reconstruction -

The longitudinal profile of extensive air showers is sensitive to the energy and type/mass of the primary particle. One of its characteristics, the atmospheric depth of shower maximum, is often used to reconstruct the elemental composition of primary cosmic rays. In this article, the impact of the atmospheric density profile on the reconstruction of the depth of maximum, as observed in fluorescence light measurements, is investigated. We consider in detail the atmospheric density profile and its time variations at the site of the southern Pierre Auger Observatory, using data that were obtained from meteorological radio soundings. Similar atmospheric effects are expected to be found also at other sites.

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arXiv2004

RHIC data and the multichain Monte Carlo DPMJET-II

Using data from RHIC we are able to systematically improve the two-component Dual Parton Model (DPM) event generator DPMJET-III. Introducing percolation parametrized as fusion of chains the model describes multiplicities and pseudorapidity distributions in nucleus-nucleus collisions at all centralities. Guided by the d-Au data from RHIC we recalibrate the model to obtain collision scaling in h-A and d-A collisions.

hep-ph↗
arXiv2004

Les Houches Guidebook to Monte Carlo Generators for Hadron Collider Physics

Recently the collider physics community has seen significant advances in the formalisms and implementations of event generators. This review is a primer of the methods commonly used for the simulation of high energy physics events at particle colliders. We provide brief descriptions, references, and links to the specific computer codes which implement the methods. The aim is to provide an overview of the available tools, allowing the reader to ascertain which tool is best for a particular application, but also making clear the limitations of each tool.

hep-ph↗
arXiv2002

BL Lac Objects in the Synchrotron Proton Blazar Model

We calculate the spectral energy distribution (SED) of electromagnetic radiation and the spectrum of high energy neutrinos from BL Lac objects in the context of the Synchrotron Proton Blazar Model. In this model, the high energy hump of the SED is due to accelerated protons, while most of the low energy hump is due to synchrotron radiation by co-accelerated electrons. To accelerate protons to sufficiently high energies to produce the high energy hump, rather high magnetic fields are required. Assuming reasonable emission region volumes and Doppler factors, we then find that in low-frequency peaked BL Lacs (LBLs), which have higher luminosities than high-frequency peaked BL Lacs (HBLs), there is a significant contribution to the high frequency hump of the SED from pion photoproduction and subsequent cascading, including synchrotron radiation by muons. In contrast, in HBLs we find that the high frequency hump of the SED is dominated by proton synchrotron radiation. We are able to model the SED of typical LBLs and HBLs, and to model the famous 1997 flare of Markarian 501. We also calculate the expected neutrino output of typical BL Lac objects, and estimate the diffuse neutrino intensity due to all BL Lacs. Because pion photoproduction is inefficient in HBLs, as protons lose energy predominantly by synchrotron radiation, the contribution of LBLs dominates the diffuse neutrino intensity. We suggest that nearby LBLs may well be observable with future high-sensitivity TeV gamma-ray telescopes.

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arXiv2002

The Composition of Cosmic Rays at the Knee

The observation of a small change in spectral slope, or 'knee' in the fluxes of cosmic rays near energies 10^15 eV has caused much speculation since its discovery over 40 years ago. The origin of this feature remains unknown. A small workshop to review some modern experimental measurements of this region was held at the Adler Planetarium in Chicago, USA in June 2000. This paper summarizes the results presented at this workshop and the discussion of their interpretation in the context of hadronic models of atmospheric airshowers.

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arXiv2000

Baryon stopping in high energy collisions in the DPMJET-III model

A new striking feature of hadron production in nuclear collisions is the large stopping of the participating nucleons in hadron-nucleus and nucleus-nucleus collisions. This enhanced baryon stopping can be understood introducing new diquark breaking mechanisms in multistring models of hadron production. Here we discuss the implementation of these diagrams into the DPMJET-III hadronic Monte Carlo model.

hep-ph↗
arXiv1999

Photomeson production in astrophysical sources

Photomeson production is the main energy loss for relativistic nucleons in dense radiation fields like the cosmic microwave background and the radiation fields in Gamma Ray Bursts (GRB) and jets of Active Galactic Nuclei (AGN). In this paper we study photomeson production in typical GRB and AGN jet radiation fields by using the recently developed Monte Carlo event generator SOPHIA (see these proceedings). We discuss processes that are relevant for the physics of cosmic ray acceleration and the production of neutrinos and gamma rays. We compare our results with widely used approximations, and find significant deviations, particularly for GRBs. The photoproduction of antibaryons as a so far not considered effect in astrophysics is briefly discussed.

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