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Publication Theoretical and Experimental Aspects of the Higgs Mechanism in the Standard Model and Beyond(2010-09) Baas, Alessandra EddaThe Standard Model of particle physics is the best existing theory for describing the interactions between elementary particles. Even though the Standard Model has been confirmed in many experiments, there remain unanswered questions. One of the main questions is how fermions and most gauge bosons get masses; the Standard Model begins with them as massless. The Higgs effect is a mechanism to explain how fermions and several gauge bosons do get masses in the Standard Model. The corresponding Higgs boson is the only particle that has not yet been detected. This Thesis gives a complete review of the Higgs effect and Higgs related topics. It starts with theoretical basics and develops the theory of the Higgs effect within the electroweak section of the Standard Model. The discussion then considers the topics of radiative corrections and the effect of the Higgs boson as a virtual particle, concentrating on the example of the rho-parameter. In addition, experimental and theoretical constraints for the Higgs mass M_H will be given with special emphasis on the Hierarchy Problem which leads to a physically unacceptable Higgs mass when using high energies (of the Grand Unification scale) as a cutoff for the radiative corrections. Furthermore experimental attempts to detect the Higgs boson at LEP2, TEVATRON and LHC will be described and the different decay channels discussed. Finally, alternative theoretical models beyond the Standard Model are motivated and presented, such as supersymmetry, a vectorlike Standard Model and a possible relation between the Higgs and the Inflaton of Cosmology.Publication Ultrafast Time-Resolved Photoluminescence Using Two-Photon Absorption(2010-09) Boge, RobertI will present a new ultrafast time-resolved photoluminescence technique using two-photon absorption detection (TPAD). In this femtosecond photoluminescence (PL) experiment the PL dynamics are monitored by focusing the PL signal and an ultrafast gate pulse on a GaN photodiode with nonlinear properties. Specifically, after sample excitation with a femtosecond excitation pulse the emitted photons from the sample and the gate pulse couple together to create electron hole pairs with the combined photon energy (two-photon absorption) in the high bandgap photodiode. The bandgap of the photodiode is large enough that linear absorption of the PL or the gate pulse is negligible. Techniques with a time resolution in the femtosecond range provide insight into dynamic processes including charge and energy relaxation, recombination and transfer. Following the discussion of the TPAD experiments I will give an overview of already existing time-resolved PL techniques which will allow to compare the performance of the presented technique with these techniques.Publication Efficiency of Parallel Tempering for Ising Systems(2010-01-01) Burkhardt, StephanThe efficiency of parallel tempering Monte Carlo is studied for a two-dimensional Ising system of length L with N=L^2 spins. An external field is used to introduce a difference in free energy between the two low temperature states. It is found that the number of replicas R_opt that optimizes the parallel tempering algorithm scales as the square root of the system size N. For two symmetric low temperature states, the time needed for equilibration is observed to grow as L^2.18. If a significant difference in free energy is present between the two states, this changes to L^1.02. It is therefore established that parallel tempering is sped up by a factor of roughly L if an asymmetry is introduced between the low temperature states. This confirms previously made predictions for the efficiency of parallel tempering. These findings should be especially relevant when using parallel tempering for systems like spin glasses, where no information about the degeneracy of low temperature states is available prior to the simulation.Publication A Neural Network based Background Supression Technique applied to Vhe Gamma Ray Data coming from the Crab Pulsar(2008-05) Reuschle, Christian AIn this thesis we present new results for the 99.9% confidence level flux upper limits on the pulsed VHE gamma ray signal coming from the Crab pulsar. In order to achieve optimum hadronic background suppression we implement a new neural network based selection technique and apply it to Cherenkov shower imaging data from the WHIPPLE 10m IACT telescope at Mount Hopkins Arizona. Special emphasis will be given to the fact that the neural network selector is trained with real data exclusively. An energy estimator for gamma ray induced extensive air shower events has been derived from Monte Carlo simulations using the Monte Carlo framework GrISU. This estimator, applied to the image data, serves as input to the neural set selector and is needed to determine the energy dependent flux upper limits. We compare our results to the results from previous studies and the performance of our neural network selection technique to the so-called Supercuts and Optimized Supercuts methods.The new flux upper limits and the new technique show the potential to settle the question about the production mechanism of pulsar radiation. However, the current analysis does not answer this question fully.Publication Designing Active Granular Squares(2016-05) Olson, Christopher CThe goal of this thesis has been to find a means of i) designing an active square particle, and ii) continuously varying its degree of activity with the objective of understanding the effects of activity on the various phases of granular matter. The motivations, results and limitations of our methods of creating active particles are discussed in this thesis. The applicability of a stochastic model based on the Langevin equation in 2D as well as implications for future experiments are also discussed.Publication Validation of Argon from Underground Sources for Use in the DarkSide-50 Detector(2015-09) Alexander, Thomas RLiquid argon is an attractive target for dark matter searches due to its low cost and exemplary event discrimination. However, atmospherically derived argon contains the beta-emitter 39Ar which confounds the growth of dual-phase time projection chamber (TPC) style detectors to the ton-scale. The DarkSide Collaboration seeks to bypass this limitation by extracting argon from deep underground, from a location known to contain significantly less 39Ar than atmospherically derived argon. This thesis will summarize the e orts taken to produce the first batch of underground argon, focusing on the first operation of the underground argon in a dual-phase TPC to validate the purity of the product, performed at Fermilab using the SCENE cryostat.Publication Bayesian Model Selection and Parameter Estimation for Gravitational Wave Signals from Binary Black Hole Coalescences(2015-09) Lombardi, Alexander LIn his theory of General Relativity, Einstein describes gravity as a geometric property of spacetime, which deforms in the presence of mass and energy. The accelerated motion of masses produces deformations, which propagate outward from their source at the speed of light. We refer to these radiated deformations as gravitational waves. Over the past several decades, the goal of the Laser Interferometer Gravitational-wave Observatory (LIGO) has been the search for direct evidence of gravitational waves from astrophysical sources, using ground based laser interferometers. As LIGO moves into its Advanced era (aLIGO), the direct detection of gravitational waves is inevitable. With the technology at hand, it is imperative that we have the tools to analyze the detector signal and examine the interesting astrophysical properties of the source. Some of the main targets of this search are coalescing compact binaries. In this thesis, I describe and evaluate bhextractor, a data analysis algorithm that uses Principal Component Analysis (PCA) to identify the main features of a set of gravitational waveforms produced by the coalescence of two black holes. Binary Black Hole (BBH) systems are expected to be among the most common sources of gravitational waves in the sensitivity band of aLIGO. However, the gravitational waveforms emitted by BBH systems are not well modeled and require computationally expensive Numerical Relativity (NR) simulations. bhextractor uses PCA to decompose a catalog of available NR waveforms into a set of orthogonal Principal Components (PCs), which efficiently select the major common features of the waveforms in the catalog and represent a portion of the BBH parameter space. From these PCs, we can reconstruct any waveform in the catalog, and construct new waveforms with similar properties. Using Bayesian analysis and Nested Sampling, one can use bhextractor to classify an arbitrary BBH waveform into one of the available catalogs and estimate the parameters of the gravitational wave source.