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Analyzing and characterizing mechanical properties of polymers is a vast field of research. In this thesis, linear and nonlinear rheological investigations have been used to study the relaxation behavior of various glass-forming liquids. In simple (non-associating and non-polymeric) liquids, the microscopic flow behavior is associated to the mass transport which is defined by the dynamics of the molecules and therefore the structural relaxation. This is usually discussed in the literatur...
In this thesis, a search for flavour-changing neutral currents in processes involving a singly produced top quark and a photon is presented. In this search, proton-proton collision data are used which were collected by the ATLAS experiment at the LHC and correspond to an integrated luminosity of 81 fb⁻¹. The top quark is assumed to decay into a b quark and a W boson, which is supposed to decay leptonically. Events are selected whose final state contains exactly one photon, one charged lepton,...
Imaging atmospheric Cherenkov telescopes (IACT) observe the sky in the highest energy ranges. From the remnants of cataclysmic supernovae to jets powered by supermassive blackholes in the center of distant galaxies, IACTs can capture the light emerging from the most extreme sources in the universe. With the recent advent of multi-messenger astronomy it has become critical for IACTs to publicly share their data and software. For the first time since the inception of IACT technology, in a...
Der neutrinolose doppelte Beta-Zerfall ist ein hypothetischer Kernzerfall dessen Nachweis grundlegende Fragen über bislang unbekannte Eigenschaften von Neutrinos liefern und auf Physik jenseits des Standard Modells der Teilchenphysik hindeuten würde. Das COBRA Experiment sucht nach diesem Zerfall mit Hilfe von CdZnTe Halbleiter-Detektoren. In dieser Arbeit wird ein wesentlich verbesserter Aufbau des Experiments, genannt Extended Demonstrator (XDEM), präsentiert. Um diesen zur verwirklich...
In this review on advanced biomolecular EPR spectroscopy, which addresses both the EPR and NMR communities, considerable emphasis is put on delineating the complementarity of NMR and EPR regarding the measurement of interactions and dynamics of large molecules embedded in fluid-solution or solid-state environments. Our focus is on the characterization of protein structure, dynamics and interactions, using sophisticated EPR spectroscopy methods. New developments in pulsed microwave and sweepab...
The World Health Organization has been listing cardiovascular disease and its sequelae as one of the leading causes of death worldwide for several years in its annual report. In general this includes all disease that originates from the vascular system and / or from the heart. Due to the high patient rate, there is great interest in researching the exact processes and effects of the diseases on the tissue as well as on the flow behavior. These can be used to develop therapeutic options, but a...
Using the existing simplified model framework, we build several dark matter models which have suppressed spin-independent scattering cross section. We show that the scattering cross section can vanish due to interference effects with models obtained by simple combinations of simplified models. For weakly interacting massive particle (WIMP) masses ≳10 GeV, collider limits are usually much weaker than the direct detection limits coming from LUX or XENON100. However, for our model combinations, ...
Starting in 2021, the LHCb experiment will switch to a fully software-based trigger system. It is an ongoing challenge to ensure that this system will be able to process events at the required rate of 30 MHz. Two alternative approaches to improve and speed up the particle track reconstruction performed in the first stage of LHCb’s software trigger are presented. An alternative method to the Kalman filter track fit inside the VELO reconstruction is presented. This method uses neural networks t...
This thesis presents the first LHCb measurement of 𝐶𝑃 violation in 𝐵0 → 𝐷∗±𝐷∓ decays. Due to the 𝑏 → 𝑐𝑐𝑑 transition, 𝐵0 → 𝐷∗±𝐷∓ decays give access to higher-order Standard Model contributions. The decay-time-dependent measurement is performed on a dataset corresponding to an integrated luminosity of 9 fb−1 recorded by the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV. The 𝐶𝑃 observables are measured with an unbinned maximum likelihood fi...
A large fraction of the gamma-ray sources presented in the Third Fermi-LAT source catalog (3FGL) is affiliated with counterparts and source types, but 1010 sources remain unassociated and 573 sources are associated with active galaxies of uncertain type. The purpose of this study is to assign blazar classes to these unassociated and uncertain sources, and to link counterparts to the unassociated. A machine learning algorithm is used for the classification, based on properties extracted from t...
Astrophysical tau neutrinos are the last unidentified standard model messenger in astroparticle physics. Their identification can open new windows to neutrino physics, improve knowledge about cosmic neutrino sources and even test physics beyond the standard model. This work aims to constrain the tau neutrino component in the astrophysical neutrino flux observed by the IceCube Neutrino Observatory. Due to neutrino oscillations over cosmic baselines, a significant fraction of tau neutrinos...
Das Ziel dieser Arbeit besteht darin, an Hand von nichtlinearer optischer Spektroskopie, Informationen über fundamentale Zustände in Halbleiter-Materialien zu erhalten. Bei diesen Zuständen handelt es sich um Anregungen von Elektron-Loch Quasiteilchen, den sogenannten Exzitonen. Diese treten im Energiebereich unterhalb der Bandlücke des Materials auf und dominieren dort die optischen Eigenschaften. Im Unterschied zur linearen Optik geschieht die Anregung in der nichtlinearen Optik durch zwei...
S5 0716+714 is a well known BL Lac object, and one of the brightest and most active blazars. The discovery in the Very High Energy band (VHE, E > 100 GeV) by MAGIC happened in 2008. In January 2015, the source went through the brightest optical state ever observed, triggering MAGIC follow-up and a VHE detection with ∼ 13σ significance (ATel ♯6999 ). Rich multiwavelength coverage of the flare allowed us to construct the broad-band spectral energy distribution of S5 0716+714 during its brightes...
This thesis is devoted to the study of mass effects in higher order radiative corrections within QED and QCD. The first part of the thesis deals with the process of deep-inelastic scattering. We compute the full mass dependence of the pure singlet Wilson coefficient in the polarized and unploarized case to next-to-leading order using iterated integrals over square root valued letters. Through explicit expansion in the asymptotic limit we proof the factorization of the heavy Wilson coefficie...
Blazars like Markarian 421 or Markarian 501 are active galactic nuclei (AGN), with their jets orientated towards the observer. They are among the brightest objects in the very high energy (VHE) gamma ray regime (>100 GeV). Their emitted gamma-ray fluxes are extremely variable, with changing activity levels on timescales between minutes, months, and even years. Several questions are part of the current research, such as the question of the emission regions or the engine of the AGN and the part...
Graphene-ferromagnet interfaces possess remarkable properties like induced magnetism in the graphene film, increased magnetic anisotropy in the ferromagnetic film, and chiral magnetism. Previously, the graphene-ferromagnet interface was investigated mainly on metallic substrates. Yet, silicon carbide (SiC) is a promising graphene substrate due to its semi-insulating properties and its industrial relevance. This thesis investigates for the first time the intercalation of thin cobalt films...
This thesis includes two parts presenting the results on the research on the deformation of ferrofluid-filled elastic capsules in external magnetic fields as well as on the possibility of the usage of swelling elastic disks as microswimmers by triggering hysteretic shape transformations. The first part is a primarily theoretical study of deformations and shape transitions of ferrofluid capsules induced by homogeneous and inhomogeneous magnetic fields. The thin elastic shell is modelled b...
Voltage control of ferromagnetism on the nanometer scale is highly appealing for the development of novel electronic devices with low power consumption, high operation speed, reliable reversibility and compatibility with semiconductor technology. Hybrid structures based on the assembly of ferromagnetic and semiconducting building blocks are expected to show magnetic order as a ferromagnet and to be electrically tunable as a semiconductor. Here, we demonstrate the electrical control of the exc...
We report on the fabrication and characterization of a novel magnetophotonic structure designed as iron garnet based magneto-optical nanoresonator cavity constrained by two noble metal mirrors. Since the iron garnet layer requires annealing at high temperatures, the fabrication process can be rather challenging. Special approaches for the protection of metal layers against oxidation and morphological changes along with a special plasma-assisted polishing of the iron garnet layer surface were ...
The effects of exchange coupling on magnetic switching properties of all-garnet multilayer thin film structures are investigated. All-garnet structures are fabricated by sandwiching a magneto-soft material of composition type Bi1.8Lu1.2Fe3.6Al1.4O12 or Bi3Fe5O12:Dy2O3 in between two magneto-hard garnet material layers of composition type Bi2Dy1Fe4Ga1O12 or Bi2Dy1Fe4Ga1O12:Bi2O3. The fabricated RF magnetron sputtered exchange-coupled all-garnet multilayers demonstrate a very attractive combina...