Flavour-tagged measurement of CP observables in B 0 s -> D∓ s K± decays with the LHCb experiment See

Röntgendiiffraktion an Papier und Vulkanfiber See

Vulkanfiber ist ein umweltfreundlicher, wiederentdeckter Werkstoff. Er wird aus nachwachsenden Rohstoffen hergestellt, ist gut zu bearbeiten, hat viele wünschenswerte Eigenschaften und ist am Ende des Produktlebenszyklus problemlos zu entsorgen. Aufgrund einiger ähnlicher Eigenschaften steht Vulkanfiber in besonderer Konkurrenz zu den erdölbasierten Kunststoffen. In dieser Arbeit wird die Struktur von Vulkanfiber und dem Ausgangsstoff Papier mittels Röntgendiffraktion untersucht. Das Mat...

The LHCb SciFi Tracker: studies on scintillating fibres and development of quality assurance procedures for the SciFi serial production See

Für das Jahr 2019 ist ein Upgrade des LHCb Detektors geplant. Die Trackingstationen hinter dem Magneten sollen dabei durch einen Detektor aus szintillierenden Fasern mit Silizium-Photomultiplier-Auslese ersetzt werden. Um die gewünschte Ortsauflösung von unter 100 µm zu erreichen, werden Fasern mit einem Durchmesser von 250 µm präzise in mehreren Lagen positioniert und zu 2.4 m langen Matten verklebt. Qualitätskontrollen während der Produktion der Fasermatten sind zwingend notwendig, um eine ...

Effective one-dimensional models including two-particle interaction from matrix product states See

In this thesis a method for deriving effective models for one-dimensional spin systems is introduced. It is based on matrix product state (MPS) and exploits translation invariance to efficiently work in the thermodynamic limit. It is tested on two analytically solvable models: The ferromagnetic spin-\textonehalf\ Heisenberg chain in an external field, and the transverse magnetic field Ising model (TFIM). The previously developed ansatz for one-particle states is extended to the descriptio...

Optical properties of vacancies in diamond at high magnetic fields See

Polarization resolved photoluminescence spectroscopy measurements are performed on defect centers in diamond. The photoluminescence of the negatively charged as well as the neutral nitrogen vacancy center shows remarkable linear polarization degrees of about 20 % at room temperature. The anisotropic angular dependence of the linear polarization characteristics mirrors the crystallographic symmetry of the defect center. In contrast to the linear polarization, the circular polarization properti...

The quest for very high energy ɣ-rays See

In this thesis a development and comparative study of a γ-Hadron separation for simulation and data measured by the First G-APD Cherenkov Telescope (FACT) is presented. The γ-Hadron separation uses a Random Forest algorithm in order to suppress the hadronic background and is evaluated on Monte Carlo simulations for the established analysis software MARS as well as for the newly developed software FACTTools. The results are applied to Crab Nebula data measured by FACT, whereas the separation ...

Deformation behavior of elastic shells and biological cells See

An elastic shell on the micro-scale filled with a suitable passive or active phase is what we refer to as a microcapsule. This work covers several classes of microcapsules spanning from static elastic shells under hydrostatic loads to animal cells made from a dynamic cytoskeleton interacting with a surrounding elastic shell. Both are microcapsules, the former enclosing a passive phase and the latter enclosing an active phase. Whereas passive microcapsules are important from a technical poin...

Structure determination of silicon nano-ribbons by means of photoelectron spectroscopy and photoelectron diffraction See

Diese Arbeit beschäftigt sich mit der Strukturbestimmung von Silizium Nano-ribbons auf einem Silber(110) Kristall und ihren Bindungseigenschaften. Silizium Nano-ribbons gehören zur Klasse der niedrigdimensionalen Strukturen, deren bekannteter Vertreter das Graphen ist. Die Struktur- und Bindungseigenschaften von Silizium Nano-ribbons sind von höchstem Interesse, da sie die elektronischen, mechanischen und optischen Eigenschaften des Materials wesentlich beeinflussen. Eine Vielzahl von Struktu...

Inverse Faraday effect and optical orientation under excitation with a train of optical pulses in solid state systems See

Ein großer Teil der wissenschaftlichen Forschung beschäftigt sich heutzutage mit möglichen Alternativen zur bisherigen Informationstechnologie. Ein heißer Kandidat sind Spin Waves (SW) um Ladungen als Informationsträger abzulösen, wodurch Ohmische Verluste verringert werden würden. Die Erzeugung durch ultrakurze Laserpulse liefert einige Vorteile gegenüber der konventionelleren Methode mit Mikrowellen-Antennen. Fokussierte Laserstrahlen dienen hier als Punktquelle der SW und erlauben die Kont...

Studies for the LHCb SciFi tracker See

The LHCb detector will undergo a major upgrade during the Long Shutdown 2 of the LHC, which will take place from 2019 to 2020. As part of the upgrade, the main tracker will be replaced by a SciFi Tracker, based on scintillating fibres read out by SiPMs. Over 100000km of fibres are needed to build the SciFi Tracker, which will extend over an area of 360m2. It will provide a spatial resolution of better than 85 μm and a detection efficiency of 98:7%. This thesis presents a series of studies on ...

Spin control and coherent optics in semiconductor nanostructures See

The thesis puts the properties of novel spintronic devices into a context with coherent optical phenomena. The first focus area deals with the magnetic manipulation of spins inside a ferromagnet-semiconductor quantum well hybrid structure. The second focus area is about optical coherence and its loss with the excitation field in InGaAs quantum dots that are embedded in microcavity structures. In previous works by it was shown that the information stored in the optical field can be transferred...

Stabilization and aggregation of preformed silver clusters in room temperature ionic liquids: a UV/Vis and X-ray absorption spectroscopy study See

Ionic liquids (ILs) have received considerable interest in various fields of research and promise a vast range of applications; among others, they are promising stabilizers for nanoparticles. ILs consist of a large organic cation and a small inorganic anion. The different charges of the molecules cause a strong attractive interaction, while the large difference of size of the molecules prevents condensation at room temperature. Due to their low vapour pressure ILs can be used under vacuum con...

Einfluss von Dotierstoffen auf die Dynamik von Eisphasen See

Wasser zählt trotz seines simplen Aufbaus zu den sonderbarsten Stoffen, die wir auf unserem Planeten Erde oder vielleicht sogar im gesamten Universum kennen. Abhängig von äußeren Konditionen wie Druck und Temperatur können unterschiedliche Phasen von Eis erzeugt werden. Zum Zeitpunkt der Erstellung dieser Arbeit sind bereits 18 kristalline Modifikationen bekannt und es werden noch weitere erwartet. Diese Dissertation befasst sich im speziellen mit dem Einfluss von Dotierstoffen auf die Dynami...

The data mining guide to the galaxy See

This thesis is concerned with the examination of Active Galactic Nuclei (AGN) within the field of gamma-ray and multi-wavelength astronomy in conjunction with data mining applications. The extension of the population of AGNs enables a tremendous refinement of our knowledge of gamma-ray emitting objects. For this purpose, the information about the class affiliation of a cataloged source and its corresponding counterparts is important. To possibly extend the AGN population, the multi-wavelengt...

Evolution and Contraction of Infinite Tensor Network States in Two-Dimensional Lattice Geometries See

The most important mathematical and physical properties of tensor networks in general as well as infinite projected entangled pair states (iPEPS) and 𝑛-simplex states are discussed in arbitrary dimensions. We review numerical methods for obtaining tensor network approximations to the ground state of local Hamiltonians including variational optimization, imaginary time evolution and the simple update scheme, mostly focusing on two-dimensional quantum systems. We demonstrate how infinite ...

Acoustic-seismic coupling of broadband signals – support for on-site inspections under the Comprehensive Nuclear Test-Ban-Treaty See

In this PhD thesis the process of acoustic-seismic coupling and a method to reduce acoustically induced soil vibrations by applying an acoustic shielding to seismic sensors are investigated. The research is motivated by the verification of the Comprehensive Nuclear-Test-Ban Treaty: During on-site inspections sensitive seismic measurements can be performed to record seismic aftershocks created in the aftermath of a large, underground, human-caused explosion. This aims to precisely localise th...

Das Phasenverhalten kolloidaler Systeme unter Druck See

Der Einfluss grundlegender thermodynamischer Größen wie Druck und Temperatur auf in Wasser gelöste Makromoleküle ist für das Verständnis vieler Prozesse des täglichen Lebens relevant. Im Zentrum dieser Arbeit steht das Verständnis des Phasenverhaltens von kolloidalen Systemen. Diese wurden hauptsächlich mit Röntgenkleinwinkelstreuung untersucht. Diese Methode ermöglicht den Zugang zur Gestalt und Wechselwirkung von Materie, deren Größe im Nanometer-Bereich liegt. Im ersten Abschnitt der Arbei...

Picosecond ultrasonics for the modulation and nanoscopy of semiconductor lasers See

Probing the standard model with rare charm decays See

This thesis comprises a study of rare charm decays in the standard model (SM) and beyond. Within an effective theory framework, we calculate the SM Wilson coefficients to (partly) next-to-next-to leading logarithmic order in quantumchromodynamics. The calculation includes matching conditions and the running of the Wilson coefficients in the renormalization group-improved perturbation theory, thereby correcting expressions used in the literature. Furthermore, a calculation of phenomenologic...