National Repository of Grey Literature 15 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
Study of high energy cosmic gamma rays
Štefánik, Stanislav ; Nosek, Dalibor (advisor) ; Soustružník, Karel (referee) ; Tománková, Lenka (referee)
In this thesis, we present our two studies focused on the detection of cosmic γ-rays and the analysis of data from γ-ray observations. One study deals with the method of the Cherenkov transparency coefficient. This method is suitable for the detector calibration in experiments employing imaging atmo- spheric Cherenkov telescopes for the indirect detection of cosmic γ-rays. Us- ing rates of recorded air showers initiated by charged cosmic rays, the method aims at the monitoring of the atmospheric transparency to Cherenkov light and the calibration of the responses of Cherenkov telescopes. We present an extension of this method for the purposes of the Cherenkov Telescope Array observatory and demonstrate its feasibility using Monte Carlo simu- lations. Our other analysis utilizes more than 7 years of data from direct γ-ray observations by the Fermi Large Area Telescope. We describe in detail signal observed from the parts of the sky around the active galactic nuclei 1ES 0229+200 and Centaurus A. We report on the findings of new astro- physical sources of high energy photons and document spectral and temporal properties of their γ-ray fluxes. 1
Study of ultra-high energy cosmic ray propagation
Fodran, Tomáš ; Nosek, Dalibor (advisor) ; Sýkora, Tomáš (referee)
The master's thesis is dedicated to studying the propagation of ultra-high energy proton cosmic rays under a hypothesis of Lorentz invariance violation. For this purpose, numerical methods were used. Our calculations indicated that the ef- fective horizon of ultra-high energy cosmic protons is significantly extended when Lorentz invariance violation is assumed. Further, we investigated the effects of Lo- rentz invariance violation on the Cosmic ray spectrum. We learned that measured cosmic ray spectra are a suitable tool for constraining the coefficients describing Lorentz invariance violation and we estimated an interval where the upper bound on the pion Lorentz invariance violating coefficient lies. Moreover, a correlation between free parameters of the analytical model of cosmic ray spectrum and coefficients, that describes Lorentz invariance violation, was found.
Energy spectrum and chemical composition of cosmic rays
Šalko, Jakub ; Nosek, Dalibor (advisor) ; Vícha, Jakub (referee)
A combined analysis of the energy spectrum and the chemical composition of ultra-high energy cosmic rays in the energy range from 1017.55 to 1019.25 eV ob- served by Pierre Auger Observatory is presented. Six different sets of primaries are considered with allowed particle fractions being determined by provided cal- culations. These calculations are based on simple assumptions about the energy spectra of primary particles and the evolution of the depth of shower maximum with energy. A simple power-law behaviour of particle spectra proved to be in- sufficient for describing the ankle in the observed all-particle energy spectrum. Assuming a broken power-law behaviour is able to reconstruct the observed all- particle energy spectrum with its ankle and the mean of the depth of shower maximum data with its break in each considered set. Including the spread of the depth of the shower maximum into calculations as quality checks suggest that provided calculations do not satisfy all relevant observables linked with chemical composition. 1
Studium kosmického záření o nejvyšších energiích
Novotný, Vladimír ; Nosek, Dalibor (advisor) ; Davídek, Tomáš (referee)
Research of the highest energy cosmic ray particles is in the middle of the interest of theoretical and experimental physics. Their energies are several orders of magnitude higher than energies accessible at present accelerators. In this work, the reconstruction techniques of extensive air showers measured at the Pierre Auger Observatory are studied. For this purpose, extensive air showers are modelled in the simulation tool CORSIKA. Data collected at the Pierre Auger Observatory together with simulations are used to calculate resolutions of reconstruction methods. The Multiple--eye reconstruction is the main interest of this work. It can be used for independent verification of experimental results of the Observatory.
Studium urychlování vysokoenergetických částic v extragalaktických objektech
Štefánik, Stanislav ; Nosek, Dalibor (advisor) ; Vorobel, Vít (referee)
Title: Study of Cosmic-Ray Acceleration in Extragalactic Objects Author: Stanislav tefnik Department: Institute of Particle and Nuclear Physics Supervisor: RNDr. Dalibor Nosek, Dr. Abstract: This thesis deals with production processes of cosmic γ-rays in astro- physical objects and methods of their detection. Possible interactions leading to the emission of high energy γ-rays in the active galaxy Centaurus A are discussed in this context. Cherenkov Telescope Array is presented as a new experiment fo- cused on the detection of air showers initiated by cosmic γ-rays. Cherenkov light of air showers is studied in the simulations done by CORSIKA simulation tool. Method of data analysis within the framework of Cherenkov telescopes is descri- bed and performed on the dataset of the active galaxy PKS 2155-304. The results include statistical tests of γ-ray source presence and its time variability. Keywords: Cosmic rays, gamma rays, astroparticle physics, high energy astro- physics, acceleration, CTA experiment
Current Status of Highest Energy Cosmic Rays
Krejčíková, Martina ; Nosek, Dalibor (advisor) ; Pěč, Viktor (referee)
The Earth is constantly bombarded by extra-high energy particles, which can not reach any man-made accelerator. Cosmic Rays have been studied over a hundred years, nevertheless we are not able to answer the questions about sources, arriving directions and composition. In the following work there are de- scribed the important projects that occupy the problems, the methods of data analysis and comparison of available experimental results. 1
Study of cosmic gamma rays
Štefánik, Stanislav ; Nedbal, Dalibor (advisor) ; Nosek, Dalibor (referee)
Title: Study of cosmic gamma rays Author: Stanislav Štefánik Department: Institute of Particle and Nuclear Physics Supervisor: Mgr. Dalibor Nedbal, Ph.D. Supervisor's e-mail address: nedbal@ipnp.troja.mff.cuni.cz Abstract: This thesis is focused on elementary knowledge of cosmic γ ray physics. In the introduction there is provided history overview of astroparticle physics, cosmic ray features and interactions are discussed. The remainder of the thesis deals with detection of cosmic γ rays with emphasis put on Čerenkov method of air shower detection. In this context the H.E.S.S. experiment in Namibia is presented and the technique of data acquisition and processing is described as well. Result of this thesis is to understand modern analysis methods used for study of cosmic rays as well as application of this method on simulated and real data acquired by H.E.S.S. Keywords: cosmic rays, gamma rays, astroparticle physics, H.E.S.S.
Highest energy cosmic ray propagation
Novotný, Vladimír ; Nosek, Dalibor (advisor) ; Nedbal, Dalibor (referee)
Research of the highest energy cosmic rays is in the middle of the interest of theoretical and experimental physics because energies that it can reach is up to nine order of magnitude higher than energies that can be reached at present accelerators. In this work we study propagation of the most energetic cosmic particles. Interactions with the cosmic background radiation and magnetic fields play the prime role of their propagation. Simulations of proton energy losses as well as simulations of energy spectra of secondary electromagnetic components and secondary neutrinos were performed. Also simulations of proton propagation in extragalactic magnetic fields were done. Program CRPropa was used to execute simulations.

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