This work investigates if and how photoelectron diffraction might become a suitable tool to measure structural changes of small molecules in the gas-phase with femtosecond temporal and angstrom spatial resolution. Molecular-frame photoelectron angular distributions (MFPAD) of O(1$s$)-, S(2$p$)- and F(1$s$)-electrons from carbonyl sulfide and fluoromethane molecules have been measured in photoelectron-photoion coincidence experiments at the synchrotron radiation sources DORIS and PETRA III (kinetic energy of photoelectrons: 16 eV < E$_{\mathrm{PE}}$ < 283 eV). [...]

It is important to exploit particle detectors for the detection and identification of electrons and photons in the best possible way, as it is adressed in this thesis by discussing three different application examples of precisely measuring electrons and photons at high-energy physics andtest beam experiments.Firstly, the optimization of the photon identification within the ATLAS detector at the LHCis investigated. Appropriate selection criteria are needed to efficiently discriminate prompt photons steming from the hard-scattering collision process from photons originating from hadronic jet decays. [...]

De novo protein design represents an exciting opportunity to explore the conformational space unsampled by nature and develop novel protein folds and functionality. One of the current challenges in the protein design field is the design of proteins that change their conformation in response to environmental cues [...]

Perovskite solar cells are a promising photovoltaic technology with their low production costsand high efficiencies. The main reason the technology is not ready for the market yet is the instability of the perovskite absorber and its fast degradation. [...]

The unique properties of x-ray free-electron lasers (XFELs), such as their immense brilliance, ultrashort pulse duration, and high photon energies, make XFELs an incredibly useful tool in a plethora of different scientific fields. Their applications include unique imaging techniques used in struc- tural biology and bio-engineering, the study of new effects in nanophysics, and the creation and probing of exotic states of matter used to investigate astrophysical objects and phenomena. [...]

The European XFEL has planned to perform pump-probe experiments by using its x-ray pulses and THz pulses. A promising concept to provide the THz pulses is to generate them using a tunable high-power accelerator-based THz source. [...]

Plasma wakefield acceleration is a promising technique for the production and/oracceleration of high energy charged particle beams on a centimeter-scale. In suchexperiments, a strong and compact focusing of divergent electron beams can berealized with an active plasma lens. [...]

he properties of the scalar boson that was first found in 2012 by the ATLAS and CMS experiments at the LHC are so far consistent with those of the Higgs boson, predicted by the Standard Model of particle physics. Further investigations of the boson's properties with increased accuracy are of immediate interest, as any deviation from Standard Model predictions could lead the way to a more fundamental theory of nature. [...]

Due to the lack of proper active gain media, mid-IR frequency combs in the molecular “fingerprint” region are normally implemented by difference frequency generation (DFG) process inside nonlinear crystals. In addition to granting an access to the long-wave (>10 μm) side of the mid-IR spectrum, DFG also offers a wide wavelength tunability, a high-repetition-rate (HRR) operation (>10 MHz), and a passive cancelation of the carrier-envelope phase offset, all of which enable a simplified experimental configuration for constructing mid-IR frequency combs.Currently, DFG-based mid-IR frequency combs especially at wavelengths beyond 10 μm suffer from insufficient available power, mainly caused by un-optimized wavelength-shifting processes and an inefficient parametric interaction of the DFG process. [...]

In this thesis we investigate two questions that shed new light on fundamentalproperties of supersymmetric gauge theories.Our first topic deals with the question, which implications results for N = 4 Super-Yang-Mills have on theories with less symmetry. Specifically we conjecture that thedilatation operator in the SU(2, 1|1) sector of any N = 1 superconformal gauge theorycan be found from the one for N = 4 Super-Yang-Mills by a redefinition of the couplingconstant. [...]

The LHC, along with all of its experiments, is going through an upgrade. The currentLHC, designed for an integrated luminosity of 300 fb$^{-1}$ , will be upgraded to the HighLuminosity LHC (HL-LHC), providing an increased collision rate and will deliver morethan 3000 fb$^{-1}$ luminosity [...]

In this work, events in which a single top quark is produced in association with a Z-boson are investigated. Particular focus is on final states in which two leptons originate from the Z boson and the top quark decays hadronically. [...]

A search for a pair of light bosons produced in decays of the 125 GeV Higgs boson, with one of the light states decaying into a pair of muons and the other into a pair of tau leptons, is presented. The search is based on a data sample corresponding to an integrated luminosity of 137.2 fb-1, collected with the CMS detector at the CERN Large Hadron Collider in the years 2016, 2017, and 2018 at a center-of-mass energy of 13 TeV. [...]

In recent years, the need for a more sustainable economic development contributed to the increasing interest in renewable energy sources. With encouraging trends on power conversion efficiencies and manufacturing costs, photovoltaics is expected to be the workhorse for the production of green energy in the future. [...]

Magnetite is a versatile transition metal oxide with applications in catalysis, biomedical imaging and spintronic devices. Moreover, magnetite nanoparticles covered with oleic acid are formed into novel nanocomposite, hierarchical materials with outstanding mechanical properties in terms of strength and hardness. [...]

A detailed study of the near-surface composition and structure of Nb, the current state-of-the-art material for superconducting radio-frequency accelerator (SRF) cavities, is of extreme importance in order to understand the consequences of different treatments applied during their production as well as its effects in conditions resembling real operation. Recently, different thermal treatments involving the presence of nitrogen achieved remarkable performance increases of such devices, however, the physical and chemical phenomena involved are still elusive. [...]

This thesis presents physics results accomplished during the 2017-2019 years in the CMS experiment. Three main contributions are discussed: a measurement of diamond sensors for the BCM1F luminometer and monitoring of its performance during the whole Run 2; a measurement of differential cross-sections of W± boson production in the muon channel as a function of pseudorapidity at $\sqrt{s}$ = 13 TeV using 2015 data set, and extraction of W± boson charge asymmetry values; a global QCD analysis with the obtained asymmetry results. [...]

In this thesis, the rst experimental determination of the running of the top quarkmass is presented. The running is extracted from a measurement of the dierentialtop quark-antiquark (tt) production cross section as a function of the invariant massof the tt system, mtt. [...]

Liquid crystals are fascinating self–assembled soft materials in which the molecules are orientationally ordered and partially positionally ordered. Liquid crystals easily response to small perturbations like the electric field, magnetic field, surface effect, etc. [...]

Extremely bright, coherent and ultra-short pulses have become recently available thanks to theavailability of X-ray Free-Electron Laser sources. Such superior beam properties allow for thefirst time to investigate non-linear phenomena in the X-ray range. [...]

In this work, the challenge to further the fundamental understanding of nanoscale matter is tackled from the perspective of cluster science. More specifically the spatial transformation of gas phase silver nanoclusters during melting is investigated. [...]

In this thesis measurements of the $t\bar{t}$ pair production at the very high transverse momentum are presented. When a top quark is produced with very high momentum the decay products are collimated in the direction of the quark, and they can be clustered within a single large cone size jet. [...]

The goal of this thesis was to enable high repetition rate Laser Wakefield Acceleration(LWFA) by solving heat induced grating deformation issues in a Chirped PulseAmplification (CPA) based 25 TW Ti:sapphire laser system centred at 800 nm. Thesepreviously limited the intensity and wavefront quality of the pulse. [...]

The interplay between intra- and intermolecular forces, with hydrogen bonding and London dispersion interactions being among the most important ones, drives bio-molecular aggregation and recognition processes. Although London dispersion interactions were described in 1930 by Fritz London, the importance of their contribution to intra- and intermolecular interactions is still not well understood at the quantitative level [...]

In this work, new concepts for solving some of the current challenges of plasma-based acceleration are proposed and explored. These concepts, which rely on a combination of plasma-acceleration stages with a magnetic chicane, show that GeV-range beams with sub-percent energy stability and an unprecedented sub-per-mille energy spread could be produced. [...]

Axionartige Teilchen sind pseudoscalare Teilchen welche in Theorien jenseits des Standardmodells vorhergesagt werden. Falls ein axionartiges Teilchen innerhalb eines kosmischen magnetischen Felds gebildet wird, wird dieses nicht durch das Hintergrundlicht absorbiert. [...]

The mammalian CLOCK:BMAL1 transcription factor complex and its coactivators CREB-binding protein (CBP)/p300 and mixed-lineage leukemia 1 (MLL1) play a central role in circadian transcriptional regulation and chromatin modification. The interactions of BMAL1’s C-terminal transactivation domain (TAD) with the KIX domain of CBP/p300 (activating) and with CRY1 (repressing) as well as the BMAL1 G-region preceding the TAD regulate the circadian oscillations [...]

Kristallographie ist die z.Zt. produktivste Methode zur Ermittlung der Struktur biologischer Moleküle. [...]

Peroxisomes are dynamic eukaryotic organelles that require import of their membrane and matrix proteins by soluble receptors in the cytosol. Their biogenesis, protein import, and proliferation are regulated by a distinct set of proteins, collectively called peroxins.Two peroxins, Pex3 and Pex19, are involved in the insertion of various Peroxisomal Membrane Proteins (PMPs) in the peroxisomal membrane and are thus crucial for its formation [...]

This thesis describes two types of light-matter interactions in magnetic thin films. In the first part, it focuses on the resonant interaction of hard X-rays with 57Fe nuclei in a microstructured magnetic element. [...]

Light is one of the most versatile tools in an experimenter’s toolbox and has been used toinvestigate the natural world since the invention of the lens and as new techniques, sources,and materials have been developed. One of the biggest turning points was the development ofa brilliant, coherent, light source: the laser. [...]

Due to the coexistence of liquid-like fluidity with conventional solidlike anisotropy, liquid crystals exhibit unique optical, dielectric or elasticproperties which make them suitable for a variety of technical andscientific applications, especially in display devices. The dielectric andelectro-optic properties of these materials, along with their phasebehaviour, are of immense importance from application perspective. [...]

Weakly Interacting Massive Particles (WIMPs) around the TeV scale have since long been among the best-motivated and most studied Dark Matter (DM) candidates. However, the absence of experimental evidence for such particles either in colliders, at telescopes or in underground laboratories, has stimulated model-building and studies of new methods of detection beyond the WIMP paradigm. [...]

In this thesis I am going to describe advanced seeding techniques to generate radiation in the region of EUV and soft X-ray and the properties of the generated radiation. I am going to focus on the echo-enabled harmonic generation (EEHG) scheme, recently shown in the soft X-ray region at the FERMI free-electron laser (FEL). [...]

The CMS detector at the LHC is foreseen to experience a major upgrade in order to cope with increased radiation flux due to the high-luminosity operation phase of the accelerator. The CMS tracker will be replaced completely, introducing a new module concept in the outer part of the subsystem, which will exploit the strong magnetic field inside the CMS detector to select high transverse momentum particles locally and send the corresponding information to the triggering system thus enhancing the efficiency of the latter.In order to allow for module prototyping and production testing, an intermediate DAQ system, referred to as μDTC, was developed in the scope of this thesis. [...]

The γ-TiAl alloys are characterized as high-temperature stable light metals. As material, they are used for blades in the low-pressure area of aircraft turbines [...]

Utrahochenergetische kosmische Strahlung (ultra-high-energy cosmic rays -- UHECR) besteht aus ionisierten Atomkernen mit den höchsten Teilchenergien, die je gemessen wurden. Zwar wurden die Quellen von UHECRs noch nicht eindeutig identifiziert, doch gibt es deutliche Anzeichen, dass sie extragalaktisch sind. [...]

In this thesis, we perform a comprehensive study of Big Bang nucleosynthesis constraints on different dark-sector models with $\mathrm{MeV}$-scale particles which are neither fully relativistic nor fully non-relativistic during all relevant temperatures. To this end, we derive a generic set of equations that can be used to determine the light-element abundances for many different dark-sector scenarios. [...]

Die morphologischen und kristallographischen Eigenschaften vertikaler, freistehender Nanodrähte, welche mittels der Dampf-Flüssigkeits-Feststoff-Methode (VLS) gezüchtet werden, sind durch ein kompliziertes Wechselspiel der Wachstumsparameter während des Herstellungsprozesses beeinflusst. Das Verständnis und die Kontrolle dieser dynamischen Prozesse sind folglich Voraussetzung für die Herstellung von Nanodrähten mit maßgeschneiderten Eigenschaften. [...]

Pulsed femtosecond (“ultrafast”) lasers are a trending tool with a vast variety of applications in science and engineering. The current trend towards more and more powerful pulsed lasers in the mid- and far-infrared spectral range enables application of established techniques, like multidimensional spectroscopy and quantum control approaches in these wavelength regimes. [...]

Water is vital for the existence of life on earth, and therefore, it is dubbed as the matrix of life. Furthermore, the hydration environment plays diverse functional, structural, and dynamic roles in molecular cell biology. [...]

Dunkle Materie bindet etwa 24 % der gesamten Energie im Universum. Bis heute ist jedoch dessen Ursprung nicht bekannt. [...]

The Standard Model of particle physics is a very successful theory, but it leaves some openquestions. Especially the topic of dark matter is a very active field of research and the discoveryof dark matter candidates might be accessible to modern collider experiments. [...]

Measurements of the luminosity and of top quark pair production in association with a Z boson ($\mathrm{t}\bar{\mathrm{t}}\mathrm{Z}$) in proton-proton collisions with the CMS experiment at the LHC are presented.The luminosity measurement of the CMS experiment is calibrated with the Van der Meer (VdM) method, based on data collected during beam separation scans. A calibration of the length scale is performed using data from constant-separation scans. [...]

The Arabidopsis thaliana E3 ubiquitin ligase SAUL1 (SENESCENCE-ASSOCIATED E3 UBIQUITIN LIGASE 1), which acts as a positive regulator during pattern-triggered immunity (PTI), is characterized by two intriguing hallmarks.(i) On the one hand, SAUL1 is guarded by two heteromeric nucleotide-binding leucine-rich repeat protein (NLR) complexes. These initiate an inducible effector-triggered immunity (ETI) in the saul1 1 mutant [...]

Natural essential oils are complex mixtures containing several compounds of structural similarity.They are well known for their wide range of applications in different areas, frommedicine to cosmetics. One of the conventional methods for their quantitative analysis is gaschromatography (GC). [...]

In this work an approach to relativistic electron acceleration employing laser-driven dielectric microstructures (DLA) is considered. New DLA designs were developed, a simulation code for efficient DLA simulation was devised, the capabilities of dielectric microstructures as particle beam diagnostic devices were investigated and a laser induced damage threshold measurement setup was implemented and tested.To leverage well developed near-infrared laser sources new DLAs were designed that are robust against realistic manufacturing tolerances and exhibit a predicted increased electron transmission of up to \SI{44}{\percent} of the charge and longitudinal acceptance of around \SI{2}{\femto\second}, but are still able to produce \SI{}{\giga\volt/\meter} acceleration gradients. [...]

A measurement of the top quark mass using LHC proton-proton collision data with an integratedluminosity of $35.9\text{fb}^{-1}$ is presented.The dataset has been recorded with the CMS detector in LHC Run 2 at a center-of-mass energyof $13$ TeV in the 2016 data taking period.Events are selected in which a top quark and a top antiquark are produced and both decay exclusively to jets.This $\text{t}\overline{\text{t}}$ all-jets final state is characterized by six jets in the detector and therefore contaminatedby multijet background, which is estimated from data in a control region.A kinematic fit is utilized to reconstruct the full $\text{t}\overline{\text{t}}$ system, improving the invariant mass resolution forthe top quark candidates and at the same time reducing the multijet background by requiring a goodness-of-fit criterion.The top quark mass is extracted using the ideogram method, simultaneously constraining an additional jet energy scale factor(JSF) to reduce systematic uncertainties.The top quark mass is found to be $m_{\text{t}}=172.34\pm0.20\,\text{(stat+JSF)}\pm0.70\,\text{(syst)}$ GeV, agreeing well with previous measurements.Furthermore, a combined top quark mass measurement using the all-jets and lepton+jets final states simultaneously isperformed.For this, a combined likelihood including the events of both final states is constructed and the same mass extractionis applied as for the all-jets final state.The resulting measurement is $m_{\text{t}}=172.26\pm0.07\,\text{(stat+JSF)}\pm0.61\,\text{(syst)}$ GeV.This is the first time a top quark mass measurement combining both final states in a single likelihood functionis presented.The result is consistent with other measurements at the LHC.A global electroweak fit employing this measurement shows the importance of the top quark mass for consistency checksof the standard model of particle physics..

Dark Matter composes a significant part of the Universe, while its physical nature remains unknown. This thesis presents two searches for Dark Matter produced in association with heavy Standard Model particles using pp collision data at a center-of-mass energy of s√=13 TeV recorded by the ATLAS detector at the Large Hadron Collider. [...]

Medium-Mn steel has drawn tremendous attention recently for automotive lightweight applications, because of its excellent combination of high strength and superior formability. The present work aims at an in-depth understanding of the process-microstructure-property relationship in medium-Mn steel. [...]

Hadronische Wechselwirkungsmodelle spielen eine zentrale Rolle in der Teilchenphysik, weil sie unter anderem zum Vergleich experimenteller Daten von durch Cherenkov-Teleskopen detektierten Luftschauern genutzt werden, um Eigenschaften des primären Luftschauerteilchens abzuleiten. In dieser Arbeit werden die beiden hadronischen Wechselwirkungsmodelle EPOS-LHC und QGSJETII-04 für gamma-ähnliche Luftschauer in deren ersten Wechselwirkung durch Monte Carlo Simulationen untersucht. [...]

In this thesis a method for electron beam slice diagnostic has been developed.The method is applicable to the drive beam of high-gain FELs operating in seededor SASE mode.It is essentially a time-resolved electron beam parameter estimationbased on experimental data on both projected and time-resolved beam propertiesand a theoretical model implemented in a numerical FEL-simulation code.This approach allows to take into account many independent measurements onelectron bunch (e.g. emittance, energy spread, current), electron optical functions,FEL-amplifier (gain length), and FEL-output radiation(wavelength, power) and deducevarious otherwise experimentally inaccessible quantities like slice parameters,initial bunching, or induced energy modulation. [...]

This thesis aims to improve the data recall efficiency from magnetic tape to disk by optimizing the request scheduling within the scientific disk storage system dCache. It is written in the context of the future data management challenges by the ATLAS experiment, where the high luminosity configuration will require an order of magnitude more storage capacity than can be provided by the current funding and usage model. [...]

Mesoscopic materials form the bridge between the quantum world of atomic systems and the classical world of macroscopic systems. The characteristic length scale of such structures is in the range of hundreds of nanometers which is comparable to visible light wavelengths. [...]

The origin of cosmic rays has been a long standing puzzle in astrophysics. Cosmic accelerators are most likely also producing high-energy neutrinos, which are not deflected by magnetic fields and can potentially reveal these sources. [...]

Since the discovery of high energetic cosmic rays their origin poses an open question. High- energy neutrino emission is considered a smoking-gun signature of cosmic ray production. [...]

Freie-Elektronen-Laser (FEL) stellen femtosekundenlange, hochintensive und kohärente Lichtpulse im XUV- und Röntgenbereich zur Verfügung. Sie ermöglichen dadurch einen Zugang zu einem zuvor unerschlossenen Parameterbereich innerhalb der Röntgenphysik und erlauben es, die Struktur und Dynamik von Materie auf natürlichen Zeit- und Längenskalen zu untersuchen. [...]

Optically generated, narrowband multi-cycle terahertz (MC-THz) radiation has the potential to revolutionize electron acceleration, X-ray free-electron lasers, advanced electron beam diagnostics and related research areas. However, the currently demonstrated THz generation efficiencies are too low to reach the requirements for many of these applications. [...]

This thesis studies the dynamics of a colloidal suspension, consisting of concentrated nan-oparticles with a silica core and a polymer shell of poly(N-isopropylacrylamide) (PNIPAm)suspended in water. The thermosresponsive polymer PNIPAm is known for its volume phasetransition at a lower critical solution temperature (LCST) of about 32−33◦C [...]

A search for pairs of light bosons produced from decays of the 125 GeV Higgs boson is presented. The search covers the light boson mass region where the particle could have an enhanced decay rate to a pair of τ leptons, according to different models and scenarios.The leptonic decay channels corresponding to the 4τ and 2μ2τ final states are used. [...]

A promising technique to measure neutrinos above 10 PeV is the detection of radio signals generated by the Askaryan effect. The effect is caused by neutrino-induced particle cascades in dense media e.g. [...]

Scanning X-ray microscopy measurements are an indespensible tool of solar cell research to-day, and the compatibility with complementary measurement modes is a particular strength. This Bachelor’s thesis investigates a series of thin-film solar cells with a Cu(In,Ga)Se2(CIGS) absorber layer that differ in their overall ratio of gallium to indium, resulting in a varyingbandgap. [...]

The Charge-density-wave (CDW) is a static modulation of the density of conduction electrons which is accompanied by a periodic distortion of the lattice. Although CDW mechanisms have been established in one-dimensional (1D) and two-dimensional (2D) systems, the driving force behind the CDW remains an enigma for three-dimensional (3D) systems. [...]

The Higgs boson is the most recent fundamental particle to be experimentally observed. Due to its large mass and its couplings to massive bosons and fermions, it has a wide variety of decay channels. [...]

In this thesis, two searches for new heavy particles with top quarks in the final stateare presented. They are based on data recorded by the CMS detector in the years 2016and 2017, respectively.In the first part of this thesis, the first search for pair-produced leptoquarks (LQs)decaying to top quarks and muons is presented [...]

This work assesses the potential of active plasma lenses to deliver stable, quality-preservingfocusing for high energy electron beams. It first provides a theoretical framework for understanding the focusing mechanisms of active plasma lenses. [...]

Molecular spintronics is an emerging research field exploiting the versatility of organic molecular electronics together with the spin degree of freedom as information carrier. Especially the use of functional organic molecules in this area opens perspective for highly integrated spintronic devices [...]

For the High-Luminosity LHC, the ATLAS Experiment will replace the current tracking system with an all-silicon detector, the Inner Tracker (ITk), consisting of inner pixel layers and outer strip layers. The ITk Strip Detector will operate in a much harsher environment than the current strip detector, the Semiconductor Tracker (SCT). [...]

The International Linear Collider is a proposed $e^{+}e^{-}$ collider with tunable centre-of-mass energies and polarised beams. By performing high-precision measurements of Standard Model observables and searches for new particles the ILC can serve as a complementary machine to the LHC.In supersymmetric extensions of the Standard Model, higgsino-like charginos and neutralinos are preferred to have masses of the order of the electroweak scale by naturalness arguments. [...]

With their brilliant short-wavelength light pulses, free-electron lasers (FEL) enable an unique insight into the interaction of light and matter. By recording scattering patterns, coherent diffractive imaging allows to image and investigate single nanometer-sized particles. [...]

With the fast technological developments of our time often new possibilities arise to gain a deeperscientific understanding of complex processes, may these be of biological, chemical or physicalnature, and materials. In natural sciences, X-ray and electron microscopy is indispensable tohelp uncovering these scientific backgrounds. [...]

The first part of this thesis investigates the direct detection of axions in particle physics. A generalized matrix formalism for describing axion-photon mixing in multi-layer systems to all orders in the axion-photon coupling is developed and applied for studying light shinning through a wall (LSW) experiments with and without dielectric layers. [...]

Liquid crystals in combination with nanoporous media, exhibiting structures significantly smaller than the wavelengths of visible light, are promising candidates to design new soft-hard photonic metamaterials. The liquid crystal provides functionality, resulting from temperature tunable anisotropic properties, i.e. [...]

A search for gluino pair production with events using 35.9 fb−1of data from ppcollisions at a center-of-mass energy of 13 TeV in 2016 is presented. Two differentcascade decay modes of gluinos are considered, and separate analyses for each of themodels are performed [...]

Tryptophan hydroxylase catalyzes the rate-limiting reaction in the biosynthesis pathway of serotonin, one of the most ubiquitous and multifunctional neurotransmitters. The influence of the serotonergic system extends over many functions of the human body, ranging from temperature and muscle tone control, to mood and sleep regulation [...]

ALPS II is a light-shining-through-a-wall experiment that will search for axion-like particles. These experiments seek to generate and measure axion-like particles in a laboratory using oscillations between photons and axions in the presence of a magnetic field. [...]

In the Minimal Supersymmetric Standard Model (MSSM), the mass of the SM-like Higgs boson can be predicted in terms of the model parameters and therefore used as a precision observable to constrain the MSSM parameter space. The precise prediction of the lightest MSSM Higgs boson mass in scenarios with one or several heavy supersymmetric particles requires the resummation of higher-order logarithmic contributions obtained within an effective-field-theory (EFT) approach. [...]

Studies of biological systems typically require the application of several complementary methods able to yield statistically-relevant results at a unique level of sensitivity. Long penetration depth of X-rays makes them particularly suitable for non-destructive volumetric investigations of whole cells and tissue sections, providing structural and elemental specificity at nanoscale spatial resolutions.X-ray ptychography is a promising imaging technique for sub-100-nm structural studies of weakly-scattering extended biological specimens. [...]

Das IceCube Neutrino Observatorium am Südpol hat die Existenz eines diffusen astrophysikalischen Neutrinoflusses nachgewiesen. Die Flavor-Zusammensetzung astrophysikalischer Neutrinos trägt Informationen über Orte kosmischer Teilchenbeschleunigung und Auswirkungen potenzieller neuer Physik auf die Neutrinoausbreitung. [...]

The medical imaging modality of X-ray fluorescence imaging (XFI), first proposed in 1986 by Boisseau, offers the possibility to utilise gold nanoparticles (GNPs) that are functionalised with specific biomarkers, offering the advantage of low dose exposure and high detection sensitivity. If these nanoparticles are injected into an organism, they can be taken up by tumour cells - a prevailing challenge for commonly used imaging modalities like computed tomography (CT) or positron emission tomography (PET), especially for early tumour diagnostics. [...]

The purpose of this thesis is to provide optimized selections for the $π^0$ reconstruction in the Belle II analysis software framework (basf2). basf2 provides generic selections on photons and on pi0s reconstructed via pi0->gg, which are designed to provide a certain pi0 reconstruction efficiency. [...]

Aligning and orienting molecules with external electric fields has long been of greatinterest in physical chemistry. Among the principle applications are various singlemolecule imaging techniques employed with the goal to determine transient molecularstructures during dynamical processes. [...]

Serial crystallography, initially developed for use at X-ray free-electron lasers, has openednew opportunities to investigate structure and dynamics of biomolecules at physiologicallyrelevant temperatures. It has since spread out to 3 rd generation synchrotron sources whereit allows us to measure protein microcrystals at room temperature, perform time-resolvedexperiments on biological crystals and obtain structures of radiation-sensitive proteins. [...]

An additional heavy Higgs boson is predicted by many models, such as the two-Higgs-doublet model (2HDM). This thesis presents a data-driven method to estimate the dominant ZZ background in the search for the decay of such a heavy scalar particle to a pair of Z bosons in the ZZ → ℓ$^+$ℓ$^−$ν$\overline{v}$ (l = electrons, muons, ν = neutrinos) final state. [...]

The existence of several neutral Higgs states is predicted in many models comprising an enlargement of the Standard Model (SM) scalar sector, notably the general Two-Higgs-Doublet Model (2HDM) and the Minimal Supersymmetric Extension of the Standard Model (MSSM). Many of these scenarios predict an enhancement of the coupling of the neutral Higgs bosons to bottom quarks. [...]

The interaction of atoms (Kr) and small molecules (CO$_2$, CH$_4$), with laser light emit- ted by different types of sources was investigated.Photoelectron spectroscopy was applied to study the two photon double ionization of krypton, induced by free electron laser (FEL) photons at 25.2 eV. Velocity map imaging (VMI) spectroscopy was also used to record the angular distributions of the photoelectrons for both the first and second ionization steps [...]

In this dissertation the concept of a new type of silicon tracking sensor called Enhanced Lateral Drift (ELAD) sensor is presented. This technology is created to meet the requirements for future linear e+e− colliders vertex and tracking detectors. [...]

The discovery of graphene in recent years has opened a research field into materials with similar electronic properties, called Dirac materials. Topological insulators and certain transition metal dichalcogenides (TMDCs) also exhibit massless and massive Dirac fermions, respectively [...]

An advent of powerful sources producing intense and ultrashort laserpulses containing high-energy photons opened up a wide range of possibilitiesto conduct experiments formerly achievable only through theoretical calculationsand models. This thesis provides a complex overview of processes which occurright after arrival of the first photons, through lattice heating, up to resolidifica-tion and formation of irreversible changes [...]

In the present work, time-resolved measurement techniques with resolutions in the femtosecond range were used to understand electronic excitations better and thus the formation and breaking of chemical bonds. Electrical excitations occur on a time scale in the attosecond to femtosecond range, and therefore ultra-short pulses in the extreme ultraviolet (XUV) range are needed to excite these processes [...]

This thesis examines collinear and transverse momentum dependent parton density functions (PDFs and TMDs) for the photon. To that end, I helped to implement the photoncontribution into the parton evolution programme uPDFevolv. [...]

Strong-field ionisation imaging offers elegant ways to measure and visualise molecular structure with picometre spatial and femtosecond temporal resolution. The underlying ionisation process is driven by an intense laser-electric field and allows to selectively extract a single electron from the outermost valence orbital(s) of the target molecule. [...]

Magnetic field sensors can be used for compass applications, to measure electrical cur-rents or to determine position and speed of objects. Layered thin-film sensors based onthe giant or tunneling magnetoresistance (GMR or TMR) are predestined for portabledevices where their small size, high effect strength and low power consumption are crucial.Through the use of oblique-incidence deposition (OID) it is possible to tailor the magneticand magnetoresistive properties of the sensors in an easy-accessible and flexible way tothe needs of an application. [...]

Laser-wakefield accelerators enable the generation of electron beams with initially nm-small emittances and GeV-level beam energies within cm-scale distances and are thereforepromissing candidates for drivers of future experiments. However, the percent-level energy-spreads and shot-to-shot fluctuations in beam quality can pose a limit to the transportability of plasma-generated beams, and further impete the measurement of the beam emittance using conventional methods.In the framework of this thesis, two energy-resolved phase-space diagnostics, a single-shot and a multi-shot method, have been implemented at the LUX laser-plasma accelerator.Electron beams from ionization injection are imaged by a compact quadrupole doublet from a virtual source into a dispersive electron spectrometer, which allows to measurethe beam emittance, beam size, divergence and phase-space correlation on the singleenergy-slice level. [...]

The advent of phase retrieval techniques has increased the resolution in X-ray microscopy by nearly an order of magnitude. With conventional imaging, X-ray microscopes cannot reach their full potential due to the lack of strong focusing options for X-rays. [...]

The Free Electron Laser in Hamburg (FLASH) has a unique combination of high repetitionrate, tunable, intense, and narrowband THz pulses naturally synchronized to the XUV pulses.It provides the opportunity to investigate light-matter interaction on an ultrafast timescale.However, due to the different properties of THz and XUV radiation, the optical transport differsfor these pulses. The result is that the optical path of the THz beamline is several meters longerthan the XUV beamline, preventing the utilization of the full potential of FLASH. [...]

The IceCube Neutrino Observatory is a cubic-kilometer in-ice Cherenkov detector located at the South Pole. At high energies, the neutrino flux of is expected to be observed in the ratio of 1 : 1 : 1 on Earth. [...]

X-ray fluorescence measurements are an ideal method for measuring the elemental distributions in samples but complications like self absorption make the evaluation of these measurements non-trivial – especially when using multiple detector modules. This is further complicated when studying low concentrations of elements, where accurate background subtraction and elemental sensitivity is essential. [...]