Search for the neutral MSSM Higgs bosons with ATLAS

The discovery of a neutral Higgs boson with large branching fractions into tau or muon pair final states would be a strong evidence of New Physics beyond the Standard Model. The discovery potential of these processes with the ATLAS detector at the Large Hadron Collider for integrated luminosities of 10 and 30 fb-1 is presented. The studies are based on the analysis of fully simulated Monte Carlo samples

Third harmonic generation in liquid core optical fibres

The objective of this thesis is to investigate third harmonic generation in liquid core fibres. Such fibres are formed by injection of liquid into a hollow, solid cladding by capillary forces. Carbon disulphide and tetrachloroethylene are identified as most promising liquid candidates. Such liquids offer a strong nonlinearity whose major contribution is non-instantaneous arising from the molecular structure. The effect of this material response during harmonic generation is investigated numerically by solving coupled evolution equations and causes distinct spectral shifts and broadening of both harmonic and fundamental wave. Both liquids offer excellent transparency and a high index of refraction enabling intermodal phase matching in a step-index geometry without requiring a complex microstructure. Aspects of fibre design and experimental realisation are presented in detail. Using sub-picosecond pump pulses of different duration the harmonic is generated in a higher order fibre mode and resulting signals are analysed in the spectral domain. Modification of the fibre cross-section towards an elliptical core is investigated. Besides the induced birefringence, harmonic generation in further sets of higher order modes is possible due to their transformation of electric fields. Design considerations of spatially modified fibres were confirmed experimentally and adaptive phase matching by controlling fibre temperature could be realised. Feasibility of long term exposure of liquid filled fibres to high average powers of femtosecond pulses is demonstrated underpinning that liquid core fibres withstand practical applications beyond laboratory use. Finally, possible routes to enhance the currently achieved conversion efficiencies for tetrachloroethylen of 2 ∙ 10^-5, and carbon disulphide of 10^-7, are identified and future prospects of this fibre platform are discussed

Search for the Neutral MSSM Higgs Bosons

The discovery of a neutral Higgs boson with large decay branching fraction to tau and muon pairs final states would be a strong evidence of New Physics beyond the Standard Model. The potential discovery of these processes with the ATLAS detector at the Large Hadron Collider is presented. The studies are based on the analysis of Monte Carlo signal and background simulated in detail through the experimental apparatus

The Discovery Potential of Neutral Supersymmetric Higgs Bosons with Decay to Tau Pairs at the ATLAS Experiment

This work presents a study of the discovery potential for the neutral supersymmetric Higgs bosons h/A/H decaying to tau pairs with the ATLAS experiment at the LHC. The study is based on Monte Carlo samples which are scaled to state-of-the-art cross sections. The analyses are designed assuming an integrated luminosity of 30 1/fb and a center-of-mass energy of sqrt(s) = 14 TeV. The results are interpreted in the mmax h benchmark scenario. Two final states are analyzed: The dileptonic channel where the two tau leptons decay to electrons or muons and the lepton-hadron channel where one tau decays to an electron or muon and the other tau decays to hadrons. The study of the dilepton channel is based completely on the detailed ATLAS simulation, the analysis of the lepton-hadron channel is based on the fast simulation. The collinear approximation is used to reconstruct the Higgs boson mass and its performance is studied. Cuts are optimized in order to discriminate the signal from background and to maximize the discovery potential given a certain Higgs boson mass hypothesis. In the lepton-hadron channel the selection is split into two analyses depending on the number of identified b-jets. Procedures to estimate the dominant backgrounds from data are studied. The shape and normalization of the Z to tautau background are estimated from Z to leptonlepton control regions. The ttbar contributions to the signal regions are estimated from ttbar control regions. The individual analyses are combined and sensitivity predictions are made depending on the Higgs boson mass mA and the coupling parameter tanβ. The light neutral MSSM Higgs bosons with mA = 150 GeV can be discovered when at least tanbeta = 11 is realized in nature. The heavy neutral MSSM Higgs bosons with mA = 800 GeV can be discovered for tanbeta ≥ 44. However, due to the large width of the reconstructed Higgs boson mass and the mass degeneration, only the sum of at least two of the three Higgs boson signals will be visible

End-to-end deep reinforcement learning in computer systems

Abstract The growing complexity of data processing systems has long led systems designers to imagine systems (e.g. databases, schedulers) which can self-configure and adapt based on environmental cues. In this context, reinforcement learning (RL) methods have since their inception appealed to systems developers. They promise to acquire complex decision policies from raw feedback signals. Despite their conceptual popularity, RL methods are scarcely found in real-world data processing systems. Recently, RL has seen explosive growth in interest due to high profile successes when utilising large neural networks (deep reinforcement learning). Newly emerging machine learning frameworks and powerful hardware accelerators have given rise to a plethora of new potential applications. In this dissertation, I first argue that in order to design and execute deep RL algorithms efficiently, novel software abstractions are required which can accommodate the distinct computational patterns of communication-intensive and fast-evolving algorithms. I propose an architecture which decouples logical algorithm construction from local and distributed execution semantics. I further present RLgraph, my proof-of-concept implementation of this architecture. In RLgraph, algorithm developers can explore novel designs by constructing a high-level data flow graph through combination of logical components. This dataflow graph is independent of specific backend frameworks or notions of execution, and is only later mapped to execution semantics via a staged build process. RLgraph enables high-performing algorithm implementations while maintaining flexibility for rapid prototyping. Second, I investigate reasons for the scarcity of RL applications in systems themselves. I argue that progress in applied RL is hindered by a lack of tools for task model design which bridge the gap between systems and algorithms, and also by missing shared standards for evaluation of model capabilities. I introduce Wield, a first-of-its-kind tool for incremental model design in applied RL. Wield provides a small set of primitives which decouple systems interfaces and deployment-specific configuration from representation. Core to Wield is a novel instructive experiment protocol called progressive randomisation which helps practitioners to incrementally evaluate different dimensions of non-determinism. I demonstrate how Wield and progressive randomisation can be used to reproduce and assess prior work, and to guide implementation of novel RL applications

Multi-Level Governance in Hitler's Germany: Reassessing the Political Structure of the National Socialist State

To explain the fatal efficiency and relative stability of the Nazi dictatorship, it is necessary to analyze how governmental institutions and society at various levels of the political system interacted. Contrary to the expectation that polycratic structures hampered administrative efficiency and tended to undermine well-established political structures it turns out that new models of governance evolved from the chaotic competition and short-lived cooperation of traditional administrations, party structures and newly created special institutions. While key players on the national level claimed to control lines of command from top to bottom the adaptability of the whole system to new challenges depended to a large extent on complex and often improvised arrangements of multi-level governance. During the war these arrangements served to integrate and to mobilize all political, administrative, military, economic and social forces whose resources were essential to sustain the war effort of the Nazi leadership