DISSERTATIONEN - MASTERARBEITEN - BACHELORARBEITEN 2019



OpenAccess [PUBDB-2019-01791] Book/Report/Dissertation / PhD Thesis

Numerical beam stability studies in external injection plasma-wakefield acceleration regimes
[DESY-THESIS-2019-005]
Hamburg : Verlag Deutsches Elektronen-Synchrotron, DESY-THESIS 177 pp. () [10.3204/PUBDB-2019-01791] = Dissertation, Universität Hamburg, 2019  GO
This work considers the phase-space evolution of an externally injectedelectron beam under various plasma-based acceleration scenariosusing numerical methods.Plasma wakefield acceleration, an exceptional technology with thepotential to drive the next generation of particle accelerators, uses aparticle driver to excite a wakefield carrying gradients in the rangeof10 GV m−1to100 GV m−1, orders of magnitude higher than theconventional cavities currently available. However, the plasma envi-ronment has stringent requirements with respect to acceptable beamparameters which need to be carefully analyzed to enable stable beamtransport and acceleration. [...]
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OpenAccess [PUBDB-2019-03086] Book/Report/Dissertation / PhD Thesis

Search for supersymmetry with tau leptons in the CMS experiment
[DESY-THESIS-2019-020]
Hamburg : Verlag Deutsches Elektronen-Synchrotron, DESY-THESIS 205 pp. () [10.3204/PUBDB-2019-03086] = Dissertation, Universität Hamburg, 2019  GO
This thesis is focused on the search for pair production of the supersymmetric $\tau$ lepton partners within the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC). The search is performed using the data collected at a center-of-mass-energy $\sqrt{s} = 13$ TeV with the CMS detector in the years 2016-2017.One of the most popular extensions of the Standard Model (SM) is supersymmetry (SUSY). [...]
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OpenAccess [PUBDB-2019-02359] Book/Report/Master Thesis

Systematic Studies of a Cavity Quench Localization System
[DESY-THESIS-2019-010]
Hamburg : Verlag Deutsches Elektronen-Synchrotron, DESY-THESIS 120 pp. () [10.3204/PUBDB-2019-02359] = Masterarbeit, Universität Hamburg, 2019  GO
Several tools for quench localization at Superconducting Radio Frequency cavities exist. One of these techniques uses the excitation of temperature waves in liquid Helium below the lambda point. [...]
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OpenAccess [PUBDB-2019-02858] Book/Report/Dissertation / PhD Thesis

Measurement and phenomenology of azimuthal correlations in high transverse momentum multi-jet topologies in CMS at the center-of-mass energy of 13 TeV
[DESY-THESIS-2019-013]
Hamburg : Verlag Deutsches Elektronen-Synchrotron, DESY-THESIS 287 pp. () [10.3204/PUBDB-2019-02858] = Dissertation, Universität Hamburg, 2019  GO
This work addresses the measurements and phenomenology of the azimuthal separation $\Delta\phi_{12}$ between the jets with the largest transverse momenta $(p_T)$ in multi-jet event topologies. The measurements are based on proton-proton collision data at the center-of-mass energy of 13 TeV recorded by the Compact Muon Solenoid (CMS) experiment in 2016, and correspond to an integrated luminosity of 35.9 fb$^{−1}$ [...]
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OpenAccess [PUBDB-2019-01768] Book/Report/Dissertation / PhD Thesis

Flavour cosmology: Electroweak baryogenesis from varying Yukawas
[DESY-THESIS-2019-004]
Hamburg : Verlag Deutsches Elektronen-Synchrotron, DESY-THESIS 168 pp. () [10.3204/PUBDB-2019-01768] = Dissertation, Universität Hamburg, 2018  GO
Despite its outstanding phenomenological successes, the Standard Model of particle physicshas a number of severe shortcomings. In this thesis, I address some of the most strikingof these. [...]
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OpenAccess [PUBDB-2019-03009] Book/Report/Dissertation / PhD Thesis

High-precision computation of observables in supersymmetric Yang–Mills theory
[DESY-THESIS-2019-019]
Hamburg : Verlag Deutsches Elektronen-Synchrotron, DESY-THESIS 149 pp. () [10.3204/PUBDB-2019-03009] = Dissertation, Universität Hamburg, 2019  GO
In this thesis we discuss modern mathematical tools for the perturbative analysis of supersymmetric Yang–Mills theories (abbreviated SYM). We apply contemporary and traditional computational techniques to two kind of problems. [...]
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OpenAccess [PUBDB-2018-05902] Dissertation / PhD Thesis

High-intracavity-power thin-disk laser for the alignment of molecules
137 pp. () [10.3204/PUBDB-2018-05902] = Dissertation, University of Hamburg, 2018  GO
The subject of this thesis was the development of a thin-disk laser with a continuous waveintracavity intensity of more than $10^{10} {W}{cm^{-2}}$ for the adiabatic alignment ofmolecules. In particular, this necessitates an intracavity power of more than 100 kW, aninternal focus with a radius of 20 µm, a well-defined and stable polarization, and benefitsfrom fundamental transverse mode operation. [...]
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[PUBDB-2019-02483] Dissertation / PhD Thesis

Vibrational dynamics in semiconductor compounds and alloys
133 pp. () = Dissertation, Friedrich-Schiller-Universität Jena, 2019
OpenAccess [PUBDB-2019-00540] Book/Report/Dissertation / PhD Thesis

High repetition rate THz characterization at 4th generation X-Ray light sources
[DESY-THESIS-2019-001]
Hamburg : Verlag Deutsches Elektronen-Synchrotron, DESY-THESIS 266 pp. () [10.3204/PUBDB-2019-00540] = Dissertation, Universität Hamburg, 2018  GO
Within this work a wholesome approach to the characterization of FEL based THz radiationis made on the example of the THz radiation provided at the THz beamline at Flash thefree electron laser at DESY in Hamburg. A SRW based model of the THz generation froma free electron and the corresponding transport is developed and used to gain insight intothe complex intensity profile created by the interplay of the THz undulator and variousmagnetic edges. [...]
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OpenAccess [PUBDB-2019-02386] Dissertation / PhD Thesis

Lithium- and oxygen-driven structural evolution in Co-free Li-Mn-rich oxides as cathodes for lithium ion batteries
Karlsruhe 121 pp. () [10.5445/IR/1000094410] = Dissertation, Karlsruhe Institute of Technology (KIT), 2019  GO
Nowadays, the lithium-rich layered 3d-transition-metal (TM) oxides (LLOs) are regarded as one of the most attractive cathode materials for next-generation lithium-ion batteries (LIBs), because they can exhibit a discharge capacity (approaching 300 mAh g$^{-1}$ at 0.1 C) much higher than that of the currently used materials(~ 180 mAh g$^{-1}$at 0.1 C). However, the formation mechanism of LLOs has not been fully understood on a fundamental level yet.One of the most interesting and still open questionsis aboutlithium and oxygen atoms are incorporatedinto the precursor’s crystal structure during the synthesisoffinal LLO products.Asystematic exploration of this subject was conducted in this PhD work. [...]
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OpenAccess [PUBDB-2019-02142] Book/Report/Dissertation / PhD Thesis

Astrophysical Implications of Self-interacting Dark Matter
[DESY-THESIS-2019-008]
Hamburg : Verlag Deutsches Elektronen-Synchrotron, DESY-THESIS 127 pp. () [10.3204/PUBDB-2019-02142] = Dissertation, Universität Hamburg, 2019  GO
In this thesis we study the astrophysical implication of self-interacting dark matter. Observations on different scales suggest the existence of an additional form of matter which interacts gravitationally. [...]
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[PUBDB-2019-01513] Bachelor Thesis
et al
Untersuchung der Magnetoptik für Harmonisches Seeding am Freien-Elektronen-Laser FLASH bei sFLASH
37 pp. () = Bachelorarbeit, University of Hamburg, 2019
OpenAccess [PUBDB-2019-01556] Book/Report/Dissertation / PhD Thesis

Study of self-modulation of an electron beam in plasma
[DESY-THESIS-2019-003]
Hamburg : Verlag Deutsches Elektronen-Synchrotron, DESY-THESIS 142 pp. () [10.3204/PUBDB-2019-01556] = Dissertation, University of Hamburg, 2018  GO
The acceleration of electron beams in plasma wakefields driven by charged particlebeams is among the most promising candidates for future TeV-scale compact electronaccelerators. Currently available high energy proton beams that could serve as driverbeams in a plasma wakefeld accelerator (PWFA) are much longer than what is requiredfor efficient excitation of high-amplitude wakefields and thus for generating the desiredhigh acceleration gradients. [...]
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OpenAccess [PUBDB-2019-02649] Book/Report/Dissertation / PhD Thesis

On accelerated expansion in string theory
[DESY-THESIS-2019-012]
Hamburg : Verlag Deutsches Elektronen-Synchrotron, DESY-THESIS 211 pp. () [10.3204/PUBDB-2019-02649] = Dissertation, Universität Hamburg, 2019  GO
In the first part of this thesis we investigate the viability of a class of models for de Sitter (dS) vacua in string theory, due to Kachru, Kallosh, Linde and Trivedi (KKLT). We start by explaining why the success or failure of such models is sensitive to a large number of Planck suppressed operators, and collect circumstantial evidence that this UV sensitivity cannot be evaded with delicately engineered models such as the Kallosh-Linde (KL) racetrack due to a generic conflict with the weak gravity conjecture (WGC) for axions. [...]
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OpenAccess [PUBDB-2019-02856] Book/Report/Dissertation / PhD Thesis

Associated Production of W + Charm in 13 TeV Proton-Proton Collisions Measured with CMS and Determination of the Strange Quark Content of the Proton
[DESY-THESIS-2019-014]
Hamburg : Verlag Deutsches Elektronen-Synchrotron, DESY-THESIS 178 pp. () [10.3204/PUBDB-2019-02856] = Dissertation, Universität Hamburg, 2019  GO
This thesis presents the measurement of associated production of a W$^±$ boson and a charm quark (W + c) in proton-proton collisions at a center-of-mass energy of 13 TeV. The data used in this analysis has been recorded by the CMS experiment at the CERN LHC and corresponds to an integrated luminosity of 35.7 fb$^{-1}$ . [...]
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OpenAccess [PUBDB-2019-02433] Master Thesis

Pseudo Nambu-Goldstone Boson Inflation
108 pp. () [10.3204/PUBDB-2019-02433] = Masterarbeit, University of Hamburg, 2019  GO
We investigate an early Universe inflationary phase driven by a pseudo Nambu-Goldstone boson. The setup is not only naturally protected in the sense of t’Hooft, but such particles are also ubiquitous in quantum and string theories. [...]
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OpenAccess [PUBDB-2019-03351] Book/Report/Dissertation / PhD Thesis

Parametric Waveform Synthesis
[DESY-THESIS-2019-021]
Hamburg : Verlag Deutsches Elektronen-Synchrotron, DESY-THESIS 172 pp. () [10.3204/PUBDB-2019-03351] = Dissertation, Universität Hamburg, 2019  GO
The coherent synthesis of pulses from Optical Parametric Amplifiers (OPAs) offers the possibility to realize field-controlled electromagnetic waveforms with sub-cycle durations, widely scalable in energy and spectral bandwidth.Here we demonstrate a fully functional prototype of a mJ-level two channel parametric waveform synthesizer, which is ready to be upgraded to three channels. The synthesized field, whose bandwidth covers more than 2 octaves, from ~500 nm to ~2200 nm, can be compressed to a non-sinusoidal sub-cycle waveform close to the transform-limit.The long term stable operation of such a complex laser source is achieved, for the first time, by means of a sophisticated optical and mechanical design of the whole OPA system, along with targeted improvements made to the commercial pump laser.A new seeding scheme based on multiple supercontinua, further scalable to the mid-IR, leads to excellent phase stability among the different OPA channels and to a simplified dispersion management scheme.A detailed study, both theoretical and experimental, of the couplings among different pulse parameters during the parametric amplification, unveiled novel details of the Carrier-Envelope-Phase (CEP) stabilization process via OPA, and guided the design of the CEP-controlled seeding front-end.A simplified two-dimensional spectral shearing interferometry setup, where the ancillary pulses are obtained by spectral filtering the pump pulses, has been developed to easily characterize the spectral phase of the ultrabroadband pulses from each channel, overcoming the limitation of second-harmonic-based methods.Furthermore, ad-hoc nonlinear optical techniques have been deployed to observe the most relevant synthesis parameters such as the CEP of the seeding pulses and the relative phase among the different channels outputs. [...]
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[PUBDB-2019-03421] Master Thesis

Confronting EFT with artificial neural networks in the quest for physics beyondthe Standard Model - Probing new paths for measuring dimension-6 operators in top-quark physics at LHC
Hamburg : University of Hamburg 1-64 () = Masterarbeit, University of Hamburg, 2019
As no sign of physics beyond the Standard Model has emerged at the Large Hadron Collider sofar, high precision measurements of particle properties and couplings become increasingly interesting.A commonly used language to interpret these measurements is effective field theory, inwhich higher-dimensional operators are added to the Standard Model. Traditional approachesmost commonly set constraints on anomalous couplings by employing and combining unfoldedmeasurements. [...]
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OpenAccess [PUBDB-2019-01182] Book/Report/Dissertation / PhD Thesis

Search for high mass higgs bosons in the final state with $b$-quarks with the CMS 2016 data
[DESY-THESIS-2019-002]
Hamburg : Verlag Deutsches Elektronen-Synchrotron, DESY-THESIS 216 pp. () [10.3204/PUBDB-2019-01182] = Dissertation, Universität Hamburg, 2019  GO
A search for high mass Higgs bosons produced in association with at least one $b$-quark and decaying into a pair of $b$-quarks using the LHC Run 2 data collected by the CMS detector is presented. The corresponding data sample was accumulated during the proton-proton collisions in 2016 at a centre-of-mass energy of $\sqrt{s} = 13$ TeV, corresponding to an integrated luminosity of 35.7 fb$^{-1}$.An extended Higgs sector containing high mass Higgs states is predicted by many theories beyond the Standard Model, such as a general two Higgs doublet model (2HDM) and its realization in the Minimal Supersymmetric extension of the Standard Model (MSSM).In many scenarios within these models Higgs couplings to $b$-quarks are significantly enhanced and therefore the final state exploited in this work is of particular interest.From the experimental point of view this final state leads to at least three highly energetic $b$-jets in the event, of which the two with the highest transverse momentum, are assumed to originate from the Higgs boson decay and another one comes from the associated production mechanism. [...]
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OpenAccess [PUBDB-2019-01602] Dissertation / PhD Thesis

Higher-Order-Mode-based Beam Phase and Beam Position Measurements in Superconducting Accelerating Cavities at the European XFEL
183 pp. () [10.3204/PUBDB-2019-01602] = Dissertation, University of Manchester, 2017  GO
Instrumentation of higher order modes (HOMs) excited in accelerating cavities for beam phase and position inference provides a noninvasive and economical beam diagnostic. The principles and techniques for this purpose are investigated for TESLA (TeV Energy Superconducting Linear Accelerator) cavities at the injector part of the newly built European XFEL and at FLASH, two free electron laser facilities based on the TESLA technology.I have designed and instrumented unconventional beam phase monitors based on monopole modes in TESLA cavities and demonstrated a routine resolution of 0.1° with a broadband setup [...]
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[PUBDB-2019-03268] Bachelor Thesis

Plasmaquellencharakterisierung für Laser- und strahlgetriebene Wakefieldbeschleuniger
Hamburg 36 pp. () = Bachelorarbeit, University of Hamburg, 2019
Plasma wakefield accelerators are able to accelerate charged particles by using the electric fieldof the free electrons within a plasma. The electric field is about one magnitude bigger thanin conventional accelerators. [...]
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OpenAccess [PUBDB-2019-02383] Dissertation / PhD Thesis

Microfluidic Sample Environments for Time-resolved Macromolecular Structure Formation Studies
Hamburg 186 pp. () [10.3204/PUBDB-2019-02383] = Dissertation, University of Hamburg, 2019  GO
This thesis deals with the polymerization-induced self-assembly (PISA) of amphiphilic blockcopolymer nano-objects, which were synthesized using a controlled radical polymerization(CRP) method, in particular, the reversible addition-fragmentation chain-transfer (RAFT)aqueous polymerization in the presence of a poly(N,N-dimethylacrylamide) stabilizer agent(macro RAFT agent). Besides the use of N-isopropylacrylamide (NIPAm) as core-formingblock for thermo-responsive nanoparticle, the aqueous dispersion polymerization of 2-methoxyethyl acrylate (MEA) was pursued as a model to study hydrophilic-hydrophobic phasetransitions: as a monomer, MEA is water-soluble. [...]
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OpenAccess [PUBDB-2019-03157] Dissertation / PhD Thesis

The magnetic properties of ultrathin Cobalt multilayers symmetrically and antisymmetrically sandwiched between layers of platinum and iridium
223 pp. () [10.3204/PUBDB-2019-03157] = Dissertation, Universität Hamburg, 2018  GO
This thesis deals with a systematic study of magnetic properties, i.e. saturation magnetization, exchange stiffness, anisotropy, interlayer exchange coupling, and average domains size, of ultrathin Co-based multilayer systems. [...]
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OpenAccess [PUBDB-2019-02167] Book/Report/Dissertation / PhD Thesis

Tau Lepton: As a Tool for Hunting Standard Model and Beyond Standard Model Higgs
[DESY-THESIS-2019-009]
Hamburg : Verlag Deutsches Elektronen-Synchrotron, DESY-THESIS 189 pp. () [10.3204/PUBDB-2019-02167] = Dissertation, Universität Hamburg, 2019  GO
This thesis presents a study of the Standard Model (SM) Higgs boson in the decay channelof ! eμ, as well as a search for neutral Minimal Supersymmetric Standard Model (MSSM)Higgs boson in the same decay channel, using data corresponding to an integrated luminosityof 35.9 fb−1 in proton-proton collisions with a center-of-mass energy of 13 TeV, collected bythe CMS detector at the Large Hadron Collider. The results of eμ channel in both analysesare combined with other channels of Higgs to decay: eh, μh and hh.An observation of the SM Higgs boson to is established with a significance of 4.9 standarddeviations, to be compared to an expected significance of 4.7 standard deviations [...]
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