Books

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. [...]

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 [...]

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. [...]

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. [...]

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. [...]

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. [...]

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. [...]

This thesis deals with the further development of the method of Borrmannspectroscopy and the development of the novel method of diffractionanomalous fine structure in Laue geometry.Borrmann spectroscopy utilizes the Borrmann effect in order to enhancethe quadrupol absorption, which enables studying weak quadrupoltransitions. In the present work a model is developed, which describes thedependence of the quadrupol enhancement on temperature and anisotropyof the chemical environment. [...]

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. [...]