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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

UHECR flux from SHDM annihilation in GC-like substructures

Wunderle, Kai Erik 14 February 2006
The objective of this thesis is to outline a relation between the measured Ultra High Energy Cosmic Ray (UHECR) flux and theoretical models for Super Heavy Dark Matter (SHDM) annihilation in Globular Cluster (GC)-like substructures in our Galaxy. Thus a possible solution for these two puzzling phenomena in present day astroparticle physics is presented. <p>A possible connection between GC-like substructures and UHECR sources was identified by combining the theoretical results for the annihilation of SHDM with the core densities derived from Dark Matter (DM)-profile fits to the GC data by Harris. The annihilation fluxes were derived for the Navarro, Frenk, and White-profile, the Moore-profile and a new constant density core approach. To compute the core densities of the GC-like substructures the GC-data by Harris were fitted to the most commonly used DM-profiles as well as to a more general DM-profile with variable inner power law index. The core densities were then calculated by making assumptions on the distribution of the masses in the GC-like substructure system as well as on the relation between the substructure mass and the core density. <p>Numerical simulations for the constant density core approach show that it is possible to reproduce the amount of substructure of the GC system of our Galaxy by choosing the mass fraction of the clumped dark matter to xi = 0.1 and the fraction of the heaviest substructure to eta = 0.01 xi, which corresponds to a mass of 10^9 M_odot for the most massive substructure. These simulation parameters then predict a product of the s-wave unitary bound with the fraction of the density of the Sun of zeta u approx 10^{-4}. Fits of the GC data to the DM-profiles reveal that all commonly used DM-profiles have to be rejected. Instead the profile with variable inner power law index is in good agreement with the GC data. The core densities are then calculated to range from 10^2 M_odot pc^{-3} to 10^8 M_odot pc^{-3}. <p>Therefore it can be concluded that SHDM annihilation in GC-like subclumps in our Galaxy presents a promising possibility to explain the measured UHECR flux.
2

UHECR flux from SHDM annihilation in GC-like substructures

Wunderle, Kai Erik 14 February 2006 (has links)
The objective of this thesis is to outline a relation between the measured Ultra High Energy Cosmic Ray (UHECR) flux and theoretical models for Super Heavy Dark Matter (SHDM) annihilation in Globular Cluster (GC)-like substructures in our Galaxy. Thus a possible solution for these two puzzling phenomena in present day astroparticle physics is presented. <p>A possible connection between GC-like substructures and UHECR sources was identified by combining the theoretical results for the annihilation of SHDM with the core densities derived from Dark Matter (DM)-profile fits to the GC data by Harris. The annihilation fluxes were derived for the Navarro, Frenk, and White-profile, the Moore-profile and a new constant density core approach. To compute the core densities of the GC-like substructures the GC-data by Harris were fitted to the most commonly used DM-profiles as well as to a more general DM-profile with variable inner power law index. The core densities were then calculated by making assumptions on the distribution of the masses in the GC-like substructure system as well as on the relation between the substructure mass and the core density. <p>Numerical simulations for the constant density core approach show that it is possible to reproduce the amount of substructure of the GC system of our Galaxy by choosing the mass fraction of the clumped dark matter to xi = 0.1 and the fraction of the heaviest substructure to eta = 0.01 xi, which corresponds to a mass of 10^9 M_odot for the most massive substructure. These simulation parameters then predict a product of the s-wave unitary bound with the fraction of the density of the Sun of zeta u approx 10^{-4}. Fits of the GC data to the DM-profiles reveal that all commonly used DM-profiles have to be rejected. Instead the profile with variable inner power law index is in good agreement with the GC data. The core densities are then calculated to range from 10^2 M_odot pc^{-3} to 10^8 M_odot pc^{-3}. <p>Therefore it can be concluded that SHDM annihilation in GC-like subclumps in our Galaxy presents a promising possibility to explain the measured UHECR flux.
3

Neutrinos from gamma-ray bursts, and the multi-messenger connection / Neutrinos von Gammablitzen und die Verbindung zu multiplen Botenteilchen

Baerwald, Philipp January 2013 (has links) (PDF)
In this work, we take a look at the connection of gamma-ray bursts (GRBs) and ultra-high-energy cosmic rays (UHECR) as well as the possibilities how to verify this connection. The currently most promising approach is based on the detection of high-energy neutrinos, which are associated with the acceleration of cosmic rays. We detail how the prompt gamma-ray emission is connected to the prediction of a neutrino signal. We focus on the interactions of photons and protons in this regard. At the example of the current ANTARES GRB neutrino analysis, we show the differences between numerical predictions and older analytical methods. Moreover, we discuss the possibilities how cosmic ray particles can escape from GRBs, assuming that UHECR are entirely made up of protons. For this, we compare the commonly assumed neutron escape model with a new component of direct proton escape. Additionally, we will show that the different components, which contribute to the cosmic ray flux, strongly depend on the burst parameters, and test the applicability on some chosen GRBs. In a further step, we continue with the considerations regarding the connection of GRBs and UHECR by connecting the GRB source model with the cosmic ray observations using a simple cosmic ray propagation code. We test if it is possible to achieve the observed cosmic ray energy densities with our simple model and what the consequences are regarding the prompt GRB neutrino flux predictions as well as the cosmogenic neutrinos. Furthermore, we consider the question of neutrino lifetime and how it affects the prompt GRB neutrino flux predictions. In a final chapter, we show that it is possible to apply the basic source model with photohadronic interactions to other types of sources, using the example of the microquasar Cygnus X-3. / In dieser Arbeit beschäftigen wir uns mit dem Zusammenhang von Gammablitzen (GRBs) und ultra-hochenergetischer kosmischer Strahlung (UHECR) sowie mit den Möglichkeiten, wie dieser Zusammenhang überprüft werden kann. Der zur Zeit erfolgsversprechendste Ansatz basiert auf der Detektion von hochenergetischen Neutrinos, die mit der Beschleunigung von kosmischer Strahlung assoziiert werden. Wir zeigen detailliert, wie die prompte Emission im Bereich der Gammastrahlung mit der Voraussage eines Neutrinosignals zusammenhängt. Ein besonderes Augenmerk legen wir hierbei auf die Wechselwirkung von Photonen und Protonen. Am Beispiel der aktuellen Analyse des ANTARES Neutrinoteleskops zu Neutrinos von Gammablitzen zeigen wir, wie sich numerische Voraussagen von älteren analytischen Methoden unterscheiden. Des Weiteren diskutieren wir Möglichkeiten, wie die Teilchen der kosmischen Strahlung aus einem Gammablitz entkommen können, wenn die ultra-hochenergetische kosmische Strahlung nur aus Protonen bestehen würde. Wir vergleichen dazu das meistens angenommene Entkommen in Form von Neutronen mit einer neuen Komponente von direkt ausströmenden Protonen. Auch zeigen wir, dass die unterschiedlichen Komponenten, die zur kosmischen Strahlung beitragen, stark von den verwendeten Parametern der Gammablitze abhängen, und uberprüfen die Modelle an einigen ausgewählten Gammablitzen. In einem weiteren Schritt führen wir die Überlegungen zu dem Zusammenhang von Gammablitzen und ultra-hochenergetischer kosmischer Strahlung fort, in dem wir mittels eines einfachen Propagationscodes für kosmische Strahlung eine Verbindung zwischen dem Quellmodell für Gammablitze und den Beobachtungsdaten der kosmischen Strahlung herstellen. Wir überprüfen, inwieweit sich die beobachteten Energiedichten der kosmischen Strahlung mittels unseres einfachen Modells realisieren lassen und welche Konsequenzen dies für die Voraussagen der prompten Neutrinoemission von Gammablitzen sowie den kosmogenischen Neutrinos hat. Außerdem gehen wir der Frage nach, wie die vorausgesagten prompten Neutrinoflüsse von einer endlichen Lebenszeit der Neutrinos beeinflusst werden würden. In einem letzten Kapitel übertragen wir das verwendete grundlegende Quellmodell mit photohadronischen Wechselwirkungen auf eine andere Klasse von Quellen, am Beispiel von Voraussagen fürden Mikroquasar Cygnus X-3.
4

An optimized mass value of dark matter particles based on ultra-high-energy cosmic rays

Hopp, Karla Marie 15 January 2007
Though the arrival directions of ultra-high-energy cosmic rays (UHECRs) are distributed in a relatively isotropic manner, there is evidence of small-scale anisotropy. This, combined with the detection of cosmic rays with energies above the GZK cut-off, has motivated us to further investigate the idea that UHECRs are the result of a top-down mechanism involving the annihilation of superheavy dark matter particles in our galactic halo. To more precisely characterize the nature of dark matter, we have endeavoured to apply two different models to the leading UHECR spectra, namely those from the AGASA, High Resolution Flys Eye, and Pierre Auger Collaborations. First, we attempt a non-linear, least-squares fit of the particle physics fragmentation function to the spectra. Second, we propose that the observed cosmic ray spectrum above 3.5 × 10E+18 eV is the superposition of flux from two different sources: bottom-up acceleration via a simple power-law relation at lower energies and scattered particles from dark matter annihilation governed by fragmentation functions at higher energies. We find that while the former model does not provide a satisfactory fit to observatory data, the latter yields reduced χ2 values between 1.14 and 2.6. From the fragmentation function component of our second model, we are able to extract estimates of dark matter particle mass. We find values of (1.2 ± 0.6) 10E+21 eV, (5.0 ± 4.3) 10E+20 eV, and (2.6 ± 1.5) 10E+21 eV respectively for the AGASA, HiRes, and Pierre Auger data, which agree with earlier predictions based on a cosmological analysis of non-thermal particle production in an inflationary universe. Furthermore, we verify that the dark matter particle densities required by our two-source model are in line with current CDM theory.
5

An optimized mass value of dark matter particles based on ultra-high-energy cosmic rays

Hopp, Karla Marie 15 January 2007 (has links)
Though the arrival directions of ultra-high-energy cosmic rays (UHECRs) are distributed in a relatively isotropic manner, there is evidence of small-scale anisotropy. This, combined with the detection of cosmic rays with energies above the GZK cut-off, has motivated us to further investigate the idea that UHECRs are the result of a top-down mechanism involving the annihilation of superheavy dark matter particles in our galactic halo. To more precisely characterize the nature of dark matter, we have endeavoured to apply two different models to the leading UHECR spectra, namely those from the AGASA, High Resolution Flys Eye, and Pierre Auger Collaborations. First, we attempt a non-linear, least-squares fit of the particle physics fragmentation function to the spectra. Second, we propose that the observed cosmic ray spectrum above 3.5 × 10E+18 eV is the superposition of flux from two different sources: bottom-up acceleration via a simple power-law relation at lower energies and scattered particles from dark matter annihilation governed by fragmentation functions at higher energies. We find that while the former model does not provide a satisfactory fit to observatory data, the latter yields reduced χ2 values between 1.14 and 2.6. From the fragmentation function component of our second model, we are able to extract estimates of dark matter particle mass. We find values of (1.2 ± 0.6) 10E+21 eV, (5.0 ± 4.3) 10E+20 eV, and (2.6 ± 1.5) 10E+21 eV respectively for the AGASA, HiRes, and Pierre Auger data, which agree with earlier predictions based on a cosmological analysis of non-thermal particle production in an inflationary universe. Furthermore, we verify that the dark matter particle densities required by our two-source model are in line with current CDM theory.
6

Advanced algorithms for Ultra-High-Energy Cosmic Ray Detection with the EUSO-TA Experiment / Avancerad algoritmer för Ultra Höga Energetiska Kosmisk strålning detektion med EUSO-TA exprimentet

Viberg, Fredrik January 2016 (has links)
Cosmic rays at energies 10^18 eV and above are known as Ultra High Energy Cosmic Rays (UHECR). UHECR are charged particles that are accelerated by the biggest accelerators in our universe. Candidate accelerators generating these UHECR are super novas, black holes and neutron stars. But where and what these intergalactic accelerators is at large still unknown. One of the experiments in the forefront of research in this eld is JEM-EUSO, a planed space based telescope for detecting UHECR particles as they enter Earth's atmosphere. Made possible by the advances in photon detectors and light weighted Fresnel lenses. A ground based path nder experiment was carried out in 2015 called EUSO-TA to test the optics and photomultiplier technologies. When the UHECR enters the atmosphere it collides with the atoms generating a number of secondary particles which in turn interacts with other atoms in the atmosphere generating a cascade of secondary particles. These trails are known as Extensive Air Showers (EAS). Mostly electrons are generated and in turn they excites the nitrogen atoms in the atmosphere which generate a isotropic characteristic uorescence light. The JEM-EUSO telescope is designed to detect and measure the photon ux. From the photon ux it will be able to estimate the energy of the initial UHECR. JEM-EUSO will cover the largest area of EAS search and increase statistics of UHECR data. This thesis describes the method and development of algorithms made for EAS analysis and detection based on EUSO-TA data. A simulation of EUSO-TA focal surface was developed, simulating background, stars and EAS. The algorithms developed involves a background subtracting lter, line detection using Hough transform and a neural network for decision making. The Hough transform is used in computer vision and is a method used to detect lines in the pictures. It successfully identi ed both simulated and captured UHECR incoming direction with small errors. Neural network are a machine learning method used classi cation and regression problems. With the use of know example data simulated or real captured data a neural network can without explicit programing it, adjust its parameters to t the data. Based on method called supervised learning. The algorithms was programed in Python and using ROOT software to build the neural network. The resulting algorithm was able to successfully detect simulated data. Test on the EUSO-TA captured data shows a promising result but has to be developed and tested further.
7

Ultra-High Energy Cosmic Rays: Composition, Early Air Shower Interactions, and <i>X</i><sub>max</sub> Skewness

Stapleton, James C. 17 August 2015 (has links)
No description available.
8

Searching for Quark Gluon Plasma Signatures in Ultra High Energy Cosmic Rays

LaHurd, Danielle V. 08 February 2017 (has links)
No description available.
9

Análise da componente fotônica dos raios cósmicos extremamente energéticos / Extremely Energetic Cosmic Rays Photonic Component Analysis

Níkolas Kemmerich 13 December 2018 (has links)
Os raios cósmicos de ultra-alta energia (UHECR) são partículas que chegam no topo da atmosfera terrestre com energia acima de 10^{18} eV. Sua composição é uma das chaves para elucidar sua origem que ainda é desconhecida. Devido ao seu baixo fluxo, os UHECR são detectados indiretamente através dos chuveiros atmosféricos extensos (EAS). Em nossa pesquisa desenvolvemos um método de discriminação da composição dos UHECR combinando dois parâmetros característicos destes chuveiros. Um deles é a profundidade na qual o chuveiro atinge seu máximo, tendo o maior número de partículas (X_{max}), e o outro, a densidade numérica de múons a 1000 m do centro do chuveiro (ho_{1000}). Temos como objetivo discriminar chuveiros iniciados por fótons daqueles iniciados por núcleos ou núcleons dado que mesmo uma pequena fração de fótons pode elucidar vários aspectos fundamentais dos UHECR. Nosso método é baseado em simulações de chuveiros, no qual, incluímos os efeitos de detecção e reconstrução, dados pelas técnicas de fluorescência e de superfície. Mostramos que nosso método de discriminação é robusto, mesmo incluindo as incertezas de reconstrução dos múons nos chuveiros que aqui estimamos para as próximas gerações de detectores de superfície. A incerteza do X_{max} será aquela usual da reconstrução pela técnica de fluorescência. Portanto, nossa análise tem um caráter preditivo para a separação da composição dos UHECR com estes parâmetros. Desta forma, nosso método pode ser aplicado aos dados dos observatórios de UHECR que utilizarem a próxima geração de detectores de superfície para reconstrução dos múons dos EAS, tais como as Colaborações Pierre Auger e Telescope Array. / Ultrahigh energy cosmic rays (UHECR) are particles which reach the Earth\'s atmosphere with energy above 10^ eV. Their composition is one of the keys to elucidate their origin which is still unknown. Due their low flux, the UHECR are detected indirectly by Extensive Air Showers (EAS). In this thesis, we develop a method to investigate their composition by simultaneously analyzing two EAS parameters, the depth at which the shower reaches its maximum size, where the number of particles reaches its maximum (X_), and the muon number at 1000 m from the shower core (ho_). We aim at discriminating EAS initiated by photons from those initiated by nucleus and nucleons. Even a small photonic fraction might reveal important fundamental UHECR questions. Our method is based on EAS simulations which includes, the detection and reconstruction by fluorescence and surface detectors. We show that our methodological approach is robust even when muons reconstruction uncertainties are considered. We derive the necessary uncertainty of the next generation of surface detectors that look for detect muons in EAS. As a result, our analysis is predictive in separating photon showers from nucleus and nucleons. Thus, our method can be used as an data analysis tool for UHECR experiments, such as the Pierre Auger Observatory and Telescope Array.
10

Análise da componente fotônica dos raios cósmicos extremamente energéticos / Extremely Energetic Cosmic Rays Photonic Component Analysis

Kemmerich, Níkolas 13 December 2018 (has links)
Os raios cósmicos de ultra-alta energia (UHECR) são partículas que chegam no topo da atmosfera terrestre com energia acima de 10^{18} eV. Sua composição é uma das chaves para elucidar sua origem que ainda é desconhecida. Devido ao seu baixo fluxo, os UHECR são detectados indiretamente através dos chuveiros atmosféricos extensos (EAS). Em nossa pesquisa desenvolvemos um método de discriminação da composição dos UHECR combinando dois parâmetros característicos destes chuveiros. Um deles é a profundidade na qual o chuveiro atinge seu máximo, tendo o maior número de partículas (X_{max}), e o outro, a densidade numérica de múons a 1000 m do centro do chuveiro (ho_{1000}). Temos como objetivo discriminar chuveiros iniciados por fótons daqueles iniciados por núcleos ou núcleons dado que mesmo uma pequena fração de fótons pode elucidar vários aspectos fundamentais dos UHECR. Nosso método é baseado em simulações de chuveiros, no qual, incluímos os efeitos de detecção e reconstrução, dados pelas técnicas de fluorescência e de superfície. Mostramos que nosso método de discriminação é robusto, mesmo incluindo as incertezas de reconstrução dos múons nos chuveiros que aqui estimamos para as próximas gerações de detectores de superfície. A incerteza do X_{max} será aquela usual da reconstrução pela técnica de fluorescência. Portanto, nossa análise tem um caráter preditivo para a separação da composição dos UHECR com estes parâmetros. Desta forma, nosso método pode ser aplicado aos dados dos observatórios de UHECR que utilizarem a próxima geração de detectores de superfície para reconstrução dos múons dos EAS, tais como as Colaborações Pierre Auger e Telescope Array. / Ultrahigh energy cosmic rays (UHECR) are particles which reach the Earth\'s atmosphere with energy above 10^ eV. Their composition is one of the keys to elucidate their origin which is still unknown. Due their low flux, the UHECR are detected indirectly by Extensive Air Showers (EAS). In this thesis, we develop a method to investigate their composition by simultaneously analyzing two EAS parameters, the depth at which the shower reaches its maximum size, where the number of particles reaches its maximum (X_), and the muon number at 1000 m from the shower core (ho_). We aim at discriminating EAS initiated by photons from those initiated by nucleus and nucleons. Even a small photonic fraction might reveal important fundamental UHECR questions. Our method is based on EAS simulations which includes, the detection and reconstruction by fluorescence and surface detectors. We show that our methodological approach is robust even when muons reconstruction uncertainties are considered. We derive the necessary uncertainty of the next generation of surface detectors that look for detect muons in EAS. As a result, our analysis is predictive in separating photon showers from nucleus and nucleons. Thus, our method can be used as an data analysis tool for UHECR experiments, such as the Pierre Auger Observatory and Telescope Array.

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