arXiv subjects

Jan Ebr

Publications and source records attributed to Jan Ebr.

29 records · Page 2Linked to original sources

arXiv2017

Mass Composition of Cosmic Rays with Combined Surface Detector Arrays

Our study exploits the Constant Intensity Cut principles applied simultaneously to muonic and electromagnetic detectors of cosmic rays. We use the fact that the ordering of events according to their signal sizes induced in different types of surface detectors provides information about the mass composition of primary cosmic-ray beam, with low sensitivity to details of hadronic interactions. Composition analysis at knee energies is performed using Monte Carlo simulations for extensive air showers having maxima located far away from a hypothetical observatory. Another type of a hypothetical observatory is adopted to examine composition of ultra-high energy primaries which initiate vertical air showers with maxima observed near surface detectors.

astro-ph.HE↗

arXiv2017

Soft Particle Production in Very High Energy Hadron Interactions

Indications of a discrepancy between simulations and data on the number of muons in cosmic ray (CR) showers exist over a large span of energies. We focus in particular on the excess of multi-muon bundles observed by the DELPHI detector at LEP and on the excess in the muon number in general reported by the Pierre Auger Observatory. Even though the primary CR energies relevant for these experiments differ by orders of magnitude, we can find a single mechanism which can simultaneously increase predicted muon counts for both, while not violating constraints from accelerators or from the longitudinal shower development as observed by the Pierre Auger Observatory. We present a brief theoretical motivation and describe a practical implementation of such a model, based on the addition of soft particles to interactions above a chosen energy threshold. Results of an extensive set of simulations show the behavior of this model in various parts of a simplified parameter space.

astro-ph.HE↗

arXiv2016

Maximum entropy analysis of cosmic ray composition

We focus on the primary composition of cosmic rays with the highest energies that cause extensive air showers in the Earth's atmosphere. A way of examining the two lowest order moments of the sample distribution of the depth of shower maximum is presented. The aim is to show that useful information about the composition of the primary beam can be inferred with limited knowledge we have about processes underlying these observations. In order to describe how the moments of the depth of shower maximum depend on the type of primary particles and their energies, we utilize a superposition model. Using the principle of maximum entropy, we are able to determine what trends in the primary composition are consistent with the input data, while relying on a limited amount of information from shower physics. Some capabilities and limitations of the proposed method are discussed. In order to achieve a realistic description of the primary mass composition, we pay special attention to the choice of the parameters of the superposition model. We present two examples that demonstrate what consequences can be drawn for energy dependent changes in the primary composition.

astro-ph.HE↗

arXiv2015

A branching model for hadronic air showers

We introduce a simple branching model for the development of hadronic showers in the Earth's atmosphere. Based on this model, we show how the size of the pionic component followed by muons can be estimated. Several aspects of the subsequent muonic component are also discussed. We focus on the energy evolution of the muon production depth. We also estimate the impact of the primary particle mass on the size of the hadronic component. Even though a precise calculation of the development of air showers must be left to complex Monte Carlo simulations, the proposed model can reveal qualitative insight into the air shower physics.

astro-ph.HE↗

arXiv2015

Real-time atmospheric monitoring for the Cherenkov Telescope Array using a wide-field optical telescope

The Cherenkov Telescope Array (CTA) is the next generation of ground-based very high energy gamma-ray instruments and is planned to be built on two sites (one in each hemisphere) in the coming years, with full array operation foreseen to begin 2020. The goal of performing high precision gamma-ray energy measurements while maximizing the use of observation time demands detailed and fast information about atmospheric conditions. Besides LIDARs designed to monitor clouds and aerosol content of the atmosphere in the pointing direction of the CTA telescopes, we propose to use the "FRAM" (F(/Ph)otometric Robotic Atmospheric Monitor) device, which is a small robotic astronomical telescope with a large field of view and a sensitive CCD camera that together ensure precise atmospheric characterization over the complete field-of-view of the CTA. FRAM will use stellar photometry to measure atmospheric extinction across the field of view of the CTA without interfering with the observation (unlike laser-based methods). This allows FRAM to operate with high temporal resolution and provide both real-time data for on-the-fly scheduling decisions and an offline database for calibration and selection of scientific data. The fast robotic mount of the telescope supports quick observation of multiple fields when the array is split and even a check of the conditions in the directions of the upcoming observations is possible. The FRAM concept is built upon experience gained with a similar device operated at the Pierre Auger Observatory. A working prototype of FRAM proposed for CTA is being built in Prague for extensive testing before deployment on site; first results and experiences with this prototype are presented.

astro-ph.IM↗

arXiv2015

Study of Dispersion of Mass Distribution of Ultra-High Energy Cosmic Rays using a Surface Array of Muon and Electromagnetic Detectors

We consider a hypothetical observatory of ultra-high energy cosmic rays consisting of two surface detector arrays that measure independently electromagnetic and muon signals induced by air showers. Using the constant intensity cut method, sets of events ordered according to each of both signal sizes are compared giving the number of matched events. Based on its dependence on the zenith angle, a parameter sensitive to the dispersion of the distribution of the logarithmic mass of cosmic rays is introduced. The results obtained using two post-LHC models of hadronic interactions are very similar and indicate a weak dependence on details of these interactions.

astro-ph.HE↗

arXiv2015

Instrumentation for comparing night sky quality and atmospheric conditions of CTA site candidates

Many atmospheric and climatic criteria have to be taken into account for the selection of a suitable site for the next generation of imaging air-shower Cherenkov telescopes, the "Cherenkov Telescope Array" CTA. Such data are not available with sufficient precision, thus a comparison of the proposed sites and final decision based on a comprehensive characterization is impossible. Identical cross-calibrated instruments have been developed which allow for precise comparison between sites, the cross-validation of existing data, and the ground-validation of satellite data. The site characterization work package of the CTA consortium opted to construct and deploy 9 copies of an autonomous multi-purpose weather sensor, incorporating an infrared cloud sensor, a newly developed sensor for measuring the light of the night sky, and an All-Sky-Camera, the whole referred to as Autonomous Tool for Measuring Observatory Site COnditions PrEcisely (ATMOSCOPE). We present here the hardware that was combined into the ATMOSCOPE and characterize its performance.

astro-ph.IM↗

arXiv2014

All Sky Camera instrument for night sky monitoring

The All Sky Camera (ASC) was developed as an universal device for a monitoring of the night sky quality and night sky background measurement. ASC system consists of an astronomical CCD camera, a fish eye lens, a control computer and associated electronics. The measurement is carried out during astronomical twilight. The analysis results are the cloud fraction (the percentage of the sky covered by clouds), night sky brightness (in mag/arcsec2) and light background in the field of view of the camera. The analysis of the cloud fraction is based on the astrometry (comparison to catalogue positions) of the observed stars.

astro-ph.IM↗

arXiv2013

All Sky Cameras for the characterization of the Cherenkov Telescope Array candidate sites

The All Sky Camera (ASC) was developed as a universal device for the monitoring of the night sky quality. Eight ASCs are already installed and measure night sky parameters at eight of the candidate sites of the Cherenkov Telescope Array (CTA) gamma-ray observatory. The ACS system consists of an astronomical CCD camera, a fish eye lens, a control computer and associated electronics. The measurement is carried out during astronomical night. The images are automatically taken every 5 minutes and automatically processed using the control computer of the device. The analysis results are the cloud fraction (the percentage of the sky covered by clouds) and night sky brightness (in mag/arcsec$^{2}$)

astro-ph.IM↗

arXiv2013

Effects of massive photons from the dark sector on the muon content in extensive air showers

Inspired by recent astrophysical observations of leptonic excesses measured by satellite experiments, we consider the impact of some general models of the dark sector on the muon production in extensive air showers. We present a compact approximative expression for the bremsstrahlung of a massive photon from an electron and use it within Monte Carlo simulations to estimate the amount of weakly interacting photon-like massive particles that could be produced in an extensive air shower. We find that the resulting muon production is by many orders of magnitude below the average muon count in a shower and thus unobservable.

astro-ph.HE↗

arXiv2012

Measurement of the proton-air cross-section at sqrt(s) = 57 TeV with the Pierre Auger Observatory

Using measured events from the fluorescence detector of the Pierre Auger Observatory, an unbiased distribution of the atmospheric slant depths where showers reach their maxima has been obtained. Analyzing the tail of this distribution the proton-air cross-section for particle production at center-of-mass energies per nucleon of 57 TeV is determined to be [505$\pm$22(stat)+28$-$36(syst)] mb. Systematic uncertainties in the analysis arise from the limited knowledge of the primary mass composition, the need to use shower simulations and the selection of events. For the purpose of making comparisons with accelerator data we also calculate the inelastic and total proton-proton cross-sections using an extended Glauber model.

hep-ex↗