Ph.D. Theses

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. [...]

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. [...]

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). [...]

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 [...]

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. [...]

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. [...]

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. [...]

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 [...]

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$^{−1}$ [...]