Ph.D. Theses

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2019-09-16
14:35
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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2019-08-30
14:05
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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2019-08-22
17:04
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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2019-08-21
13:04
OpenAccess [PUBDB-2019-03055] Dissertation / PhD Thesis

Precious metal based bulk glass-forming liquids : development, thermodynamics, kinetics and structure
Universität des Saarlandes 132 pp. () [10.22028/D291-27993] = Dissertation, Saarland University, 2019  GO
Bulk glass-forming alloy compositions are found in various noble-metal based systems. Their superior properties and their high noble metal content predestinate these alloy classes for the application as jewelry alloys [...]
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2019-08-14
13:31
OpenAccess [PUBDB-2019-03011] Book/Report/Dissertation / PhD Thesis

Electron-beam diagnostics for a laser-driven plasma wakefield accelerator in the framework of FLASHForward
[DESY-THESIS-2019-015]
Hamburg : Verlag Deutsches Elektronen-Synchrotron, DESY-THESIS 139 pp. () [10.3204/PUBDB-2019-03011] = Dissertation, Universität Hamburg, 2018  GO
Plasma wakefields are a promising approach for the acceleration of electrons with ultrahigh (10 to 100 GV/m) electric fields. Nowadays, high-intensity laser pulses are routinely utilized to excite these large-amplitude plasma waves. [...]
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2019-08-13
20:50
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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2019-08-13
11:36
OpenAccess [PUBDB-2019-02996] Dissertation / PhD Thesis

Position Resolution and Upgradeof the CMS Pixel Detector andSearch for the Higgs Boson in the $\tau^+ \tau^-$ Final State
2015 pp. () [10.3204/PUBDB-2019-02996] = Dissertation, Karlsruhe Institute of Technology, 2014  GO
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2019-08-13
11:17
OpenAccess [PUBDB-2019-02995] Dissertation / PhD Thesis

Search for SUSY in Same-Sign Di-LeptonEvents with the CMS Detector
160 pp. () [10.3204/PUBDB-2019-02995] = Dissertation, Hamburg University, 2012  GO
In this thesis a search for new physics is presented, based on events with two isolated same sign leptons (muons and electrons), jets, and missing transverse energy. The analyzed data corresponds to an integrated luminosity of 1.1 fb$^{-1}$ and is collected with the CMSdetector in proton-proton collisions at the LHC with a center-of-mass energy of 7TeV. [...]
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2019-08-13
11:11
OpenAccess [PUBDB-2019-02993] Dissertation / PhD Thesis

Higher Order QCD Radiation in Top Pair Production with the CMS Detector
142 pp. () [10.3204/PUBDB-2019-02993] = Dissertation, Hamburg University, 2009  GO
The Large Hadron Collider at CERN will collide protons with a centre-of-massenergy of up to $√_s =$ 14TeV, thereby offering the opportunity to explore a widerange of physics topics.In this thesis the effects of QCD radiation in top pair events are examined.Due to the large top mass, top pairs are well suited for an investigation of gluonemissions. An extensive study comparing different radiation models implementedin Monte Carlo event generators is presented [...]
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2019-07-29
13:31
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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