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Measurement of the proton structure from high-Q2 neutral current events in e+p deep inelastic scattering at HERASchnurbusch, Henning. Unknown Date (has links) (PDF)
University, Diss., 2002--Bonn.
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Measurement of high-Q-1hn2 charged current cross sections in e+p deep inelastic scattering at HERARautenberg, Julian. Unknown Date (has links) (PDF)
University, Diss., 2004--Bonn.
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Measurement of D*+- production at low Q2 with the beam pipe calorimeter of ZEUS at HERAIrrgang, Peter. Unknown Date (has links) (PDF)
University, Diss., 2004--Bonn.
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Search for supersymmetry in events containing light leptons, jets and missing transverse momentum in \(\sqrt{s}\) = 8 TeV pp collisions with the ATLAS detector / Suche nach Supersymmetrie in Ereignissen mit leichten Leptonen, Jets und fehlendem Transversalimpuls in pp-Kollisionen bei \(\sqrt{s}\) = 8 TeV mit dem ATLAS-DetektorSchreyer, Manuel January 2015 (has links) (PDF)
The results of two analyses searching for supersymmetry (SUSY) in data of the ATLAS experiment are presented in this thesis. The data were recorded in proton-proton collisions at the Large Hadron Collider in 2012 at a centre of mass energy of \(\sqrt{s}\)=8 TeV and correspond to an integrated luminosity of 20.3 fb\(^{−1}\). The first search is performed in signatures containing an opposite-sign electron or muon pair, which is compatible with originating from a Z boson decay, in addition to jets and large missing transverse momentum. The analysis targets the production of squarks and gluinos in R-parity conserving (RPC) models with SUSY breaking via General Gauge Mediation (GGM). The main Standard Model (SM) backgrounds are \(t\overline t\), WW, W+t and Z to \(\tau \tau\) processes which are entirely estimated from data using different-flavour events. Besides that, the SM production of Z bosons in association with jets and large fake missing momentum from mismeasurements plays a role and is predicted with the data-driven jet smearing method. Backgrounds from events with fake leptons are estimated with the data-driven matrix method. WZ/ZZ production as well as smaller background contributions are determined from Monte-Carlo simulations. The search observes an excess of data over the SM prediction with a local significance of 3.0 \(\sigma\) in the electron channel, 1.7 \(\sigma\) in the muon channel and 3.0 \(\sigma\) when the two channels are added together. The results are used to constrain the parameters of the GGM model. The second analysis uses the already published results of an ATLAS search for SUSY in events with one isolated electron or muon, jets and missing transverse momentum to reinterpret them in the context of squark and gluino production in SUSY models with R-parity violating (RPV) \(LQ\overline D\)-operators. In contrast to RPC models, the lightest SUSY particle (LSP) is not stable but decays into SM particles. "Standard" analyses often do not consider SUSY models with RPV although they are in principle sensitive to them. The exclusion limits on the squark and gluino mass obtained from the reinterpretation extend up to 1200 GeV. These are the first results by any ATLAS SUSY search which systematically cover a wide range of RPV couplings in the case of prompt LSP decays. However, the analysis is not sensitive to the full parameter space of the \(LQ\overline D\)-model and reveals gaps in the ATLAS SUSY program which have to be closed by dedicated search strategies in the future. / In dieser Arbeit werden die Ergebnisse von zwei Suchen nach Supersymmetrie (SUSY) in Daten des ATLAS-Experiments präsentiert. Die Messdaten wurden im Jahr 2012 in Proton-Proton-Kollisionen am Large Hadron Collider bei einer Schwerpunktsenergie von \(\sqrt{s}\) = 8 TeV gewonnen und entsprechen einer integrierten Luminosität von 20,3 fb\(^{−1}\). Die erste Suche verwendet Signaturen mit Jets, großem fehlenden Transversalimpuls sowie einem Elektron- oder Myonpaar mit entgegengesetzter Ladung, dessen Eigenschaften mit einem Leptonpaar aus dem Zerfall eines Z-Bosons vereinbar sind. Die Analyse zielt auf die Untersuchung von Squark- und Gluinoproduktion im Rahmen R-paritätserhaltender (RPC) Modelle mit SUSY-Brechung durch General Gauge Mediation (GGM) ab. Die Hauptuntergründe des Standardmodells (SM) sind \(t\overline t\), WW, W+t und Z nach \(\tau \tau\) Prozesse. Diese werden komplett aus den Daten selbst unter Verwendung von Ereignissen mit Leptonpaaren unterschiedlichen Flavours abgeschätzt. Daneben spielt der Untergrund aus der SM-Produktion von Z-Bosonen in Verbindung mit Jets und großem fehlenden Impuls, der durch Fehlmessungen fälschlicherweise rekonstruiert wird, ein Rolle. Dieser wird mit der datengestützten Jet-Smearing-Methode abgeschätzt. Der Hintergrundbeitrag von Ereignissen mit fehlidentifizierten Leptonen wird mit der datengestützten Matrix-Methode bestimmt, während die Produktion von WZ/ZZ-Paaren sowie kleinere Untergrundprozesse mit Hilfe von Monte-Carlo-Simulationen abgeschätzt werden. Die Suche beobachtet einen Überschuss an Daten über der SM-Vorhersage mit einer lokalen Signifikanz von 3,0 \(\sigma\) im Elektronkanal, 1,7 \(\sigma\) im Myonkanal und 3,0 \(\sigma\), wenn beide Kanäle zusammengezählt werden. Mit den Ergebnissen lassen sich die Parameter des GGM-Modells einschränken. Die zweite Analyse interpretiert die bereits veröffentlichten Ergebnisse einer ATLAS SUSY-Suche in Ereignissen mit einem isolierten Elektron oder Myon, Jets und fehlendem Transversalimpuls im Rahmen von Squark- und Gluinoproduktion in SUSY-Modellen, in denen die R-Parität durch \(LQ\overline D\)-Operatoren verletzt wird. Im Gegensatz zu RPC-Modellen ist das leichteste SUSY-Teilchen (LSP) dort nicht stabil, sondern zerfällt in SM-Teilchen. R-paritätsverletzende (RPV) SUSY-Modelle werden von "Standardanalysen" oft vernachlässigt, obwohl diese prinzipiell sensitiv auf RPV SUSY sind. Die Ausschlussgrenzen auf die Squark- und Gluinomasse, die sich aus der Reinterpretation ergeben, reichen bis zu 1200 GeV. Dies sind die ersten derartigen Ergebnisse einer ATLAS SUSY-Suche, die einen großen Bereich möglicher RPV-Kopplungen für den Fall prompter LSP-Zerfälle auf systematische Art und Weise abdecken. Allerdings ist die Analyse nicht im gesamten Parameterraum des \(LQ\overline D\)-Modells sensitiv und deckt somit Lücken im ATLAS SUSY-Programm auf. Diese sollten in Zukunft durch speziell optimierte Suchstrategien geschlossen werden.
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Intercomparison of shortwave radiative transfer schemes in global aerosol modelingRandles, Cynthia A., Kinne, Stefan, Myhre, Gunnar, Schulz, Michael, Stier, Philip, Fischer, Jürgen, Doppler, Lionel, Highwood, Eleanor, Ryder, Claire, Harris, Bethan, Huttunen, Jani, Ma, Y., Pinker, Rachel T., Mayer, Bernhard, Neubauer, David, Hitzenberger, Regina, Oreopoulos, Lazaros, Lee, Dongmin, Pitari, Giovanni, Di Genova, Glauco, Quaas, Johannes, Rose, Fred G., Kato, Seiji, Rumbold, Steve T., Vardavas, Ilias, Hatzianastassiou, Nikos, Matsoukas, Christos, Yu, Hongbin, Zhang, F., Zhang, Hua, Lu, P. 25 August 2015 (has links) (PDF)
In this study we examine the performance of 31 global model radiative transfer schemes in cloudfree conditions with prescribed gaseous absorbers and no aerosols (Rayleigh atmosphere), with prescribed scatteringonly aerosols, and with more absorbing aerosols. Results are compared to benchmark results from high-resolution, multiangular line-by-line radiation models. For purely scattering
aerosols, model bias relative to the line-by-line models in the top-of-the atmosphere aerosol radiative forcing ranges from roughly −10 to 20 %, with over- and underestimates of radiative cooling at lower and higher solar zenith angle, respectively. Inter-model diversity (relative standard deviation) increases from ~ 10 to 15% as solar zenith angle decreases. Inter-model diversity in atmospheric and surface forcing decreases with increased aerosol absorption, indicating that the treatment of multiple-scattering is more variable
than aerosol absorption in the models considered. Aerosol
radiative forcing results from multi-stream models are generally
in better agreement with the line-by-line results than the
simpler two-stream schemes. Considering radiative fluxes,
model performance is generally the same or slightly better
than results from previous radiation scheme intercomparisons.
However, the inter-model diversity in aerosol radiative
forcing remains large, primarily as a result of the treatment of
multiple-scattering. Results indicate that global models that
estimate aerosol radiative forcing with two-stream radiation
schemes may be subject to persistent biases introduced by
these schemes, particularly for regional aerosol forcing.
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Development and Characterization of a tunable ultrafast X-ray source via Inverse Compton ScatteringJochmann, Axel 29 October 2014 (has links) (PDF)
Ultrashort, nearly monochromatic hard X-ray pulses enrich the understanding of the dynamics and function of matter, e.g., the motion of atomic structures associated with ultrafast phase transitions, structural dynamics and (bio)chemical reactions. Inverse Compton backscattering of intense laser pulses from relativistic electrons not only allows for the generation of bright X-ray pulses which can be used in a pumpprobe experiment, but also for the investigation of the electron beam dynamics at the interaction point.
The focus of this PhD work lies on the detailed understanding of the kinematics during the interaction of the relativistic electron bunch and the laser pulse in order to quantify the influence of various experiment parameters on the emitted X-ray radiation.
The experiment was conducted at the ELBE center for high power radiation sources using the ELBE superconducting linear accelerator and the DRACO Ti:sapphire laser system. The combination of both these state-of-the-art apparatuses guaranteed the control and stability of the interacting beam parameters throughout the measurement.
The emitted X-ray spectra were detected with a pixelated detector of 1024 by 256 elements (each 26μm by 26μm) to achieve an unprecedented spatial and energy resolution for a full characterization of the emitted spectrum to reveal parameter influences and correlations of both interacting beams. In this work the influence of the electron beam energy, electron beam emittance, the laser bandwidth and the energy-anglecorrelation on the spectra of the backscattered X-rays is quantified.
A rigorous statistical analysis comparing experimental data to ab-initio 3D simulations enabled, e.g., the extraction of the angular distribution of electrons with 1.5% accuracy and, in total, provides predictive capability for the future high brightness hard X-ray source PHOENIX (Photon electron collider for Narrow bandwidth Intense X-rays) and potential all optical gamma-ray sources.
The results will serve as a milestone and starting point for the scaling of the Xray flux based on available interaction parameters of an ultrashort bright X-ray source at the ELBE center for high power radiation sources. The knowledge of the spatial and spectral distribution of photons from an inverse Compton scattering source is essential in designing future experiments as well as for tailoring the X-ray spectral properties to an experimental need.
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Finite lifetime effects in top quark pair production at thresholdReisser, Christoph Josef January 2008 (has links)
Zugl.: München, Techn. Univ., Diss., 2008
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Production of sleptons in e-e-collisionsWagner, Alexander. Unknown Date (has links) (PDF)
Würzburg, University, Diss., 2008.
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A polarized discrete ordinate scattering model for radiative transfer simulations in spherical atmospheres with thermal sourceEmde, Claudia January 2005 (has links) (PDF)
Zugl.: Bremen, Univ., Diss., 2005
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Wachstum epitaktischer CoSi 2 -Schichten durch Reaktion metallischer Doppelschichten mit Si(100)Gebhardt, Barbara. January 1999 (has links)
Chemnitz, Techn. Univ., Diss., 1999.
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