This thesis describes a detailed research for the decay B°s (r) J/ψh, within data taken from p collisions at √s=1.8TeV. Proton anti-proton collisions contain many different physics processes. From these processes many are of lesser interest. The trigger logic specific to selecting a sample of data rich in processes relevant to this particular study is described in detail. The analysis method proceeds as follows. The simulation program used to model acceptances of B+ (r) J/ψK+ and B°s (r) J/ψh samples is described. Within this description theoretical inputs and assumptions made are given in detail. Constraints made on each generated sample are then outlined. From the simulation, the discussion turns to the reconstruction of B+ (r) J/ψK+ and the search for B°s (r) J/ψh within the CDF data. All stages of data selection are discussed. The analysis then turns to acceptance and efficiency factors considered. Specific effort is made to fully describe the photon reconstruction efficiency. Photon reconstruction efficiency is studied in the CDF environment by introducing a data based Monte Carlo program. This detailed simulation is discussed and final photon reconstruction efficiencies are given. Systematic uncertainties are analysed in detail. The generator level simulation is used to provide error propagation for acceptance and efficiency parameterisations introduced. Systematic uncertainties from the analysis of data are also given. The results of the B (r) J/ψK+ reconstruction and the search for B°s (r) J/ψh are given. From an integrated luminosity of 110pb-1, 1178171 J/ψ (r) m+ m- events were collected. 490 ± 23 B+ (r) J/ψK+ events were isolated. From the sample of J/ψ(r) m+m- events a branching ratio limit of B(B°s (r) J/ψh) < 6.3 x 10-3 is set at a 90% confidence limit.

Als erste kommerziell verfügbare Technologie der Quanteninformation ermöglicht die Quanten-Schlüsselverteilung eine sichere Datenübertragung indem einzelne Photonen oder quantenmechanisch verschränkte Photonenpaare zur Erzeugung eines Schlüssels verwendet werden. Die hierfür benötigten nicht-klassischen Photonen-Zustände können durch Halbleiter-Quantenpunkte erzeugt werden. Im Gegensatz zu anderen Quanten-Emittern wie isolierten Atomen, organischen Molekülen oder Fehlstellen in Diamantnanokristallen bieten diese zudem den Vorteil, direkt in komplexe Halbleiter-Mikrostrukturen integriert werden zu können. Quantenpunkte sind somit prädestiniert für die Entwicklung neuartiger optoelektronischer Bauelemente auf einer skalierbaren Technologieplattform. Vor diesem Hintergrund werden in der vorliegenden Arbeit die Eigenschaften elektrisch gepumpter Quantenpunkt-Mikrostrukturen untersucht. Als optisch aktives Medium dienen dabei selbstorganisierte InAs/GaAs-Quantenpunkte. Die Zielsetzung ist die Erzeugung nicht-klassischen Lichts für Anwendungen in der Quantenkommunikation, wobei ein besonderer Fokus auf dem elektrischen Betrieb der entsprechenden Quantenlichtquellen liegt. Dabei werden sowohl ausgeprägte Resonatoreffekte im Regime der schwachen Licht-Materie-Wechselwirkung ausgenutzt, um helle Einzelphotonenquellen zu realisieren, als auch die Eigenschaften korrelierter Photonenpaare zweier spektral separierter Quantenpunkt-Zustände analysiert. Als Untersuchungsmethode wird in erster Linie die spektral und zeitlich hochauflösende Mikro-Lumineszenz-Spektroskopie bei kryogenen Temperaturen eingesetzt. Zudem erfolgen Experimente zur Photonenstatistik anhand von Messungen der Auto- sowie Kreuzkorrelationsfunktion zweiter Ordnung. Wie im Folgenden aufgeführt, gelingt dabei der Bogenschlag von grundlegenden Untersuchungen an Quantenpunkt-Mikrostrukturen bis hin zur erstmaligen Implementierung elektrisch getriggerter Quantenpunkt-Einzelphotonenquellen in realistischen Experimenten zur Quanten-Schlüsselverteilung außerhalb einer geschützten Laborumgebung. Elektrisch getriggerte Einzelphotonenquellen: Für die Erzeugung elektrisch getriggerter, einzelner Photonen wurden Quantenpunkte in Mikroresonatoren eingebettet. Diese basieren auf dotierten, zylindrischen Fabry-Pérot Mikrosäulenresonatoren, deren Design bezüglich der Photonen-Auskoppeleffizienz optimiert wurde. […] Anhand von Messungen zur Photonenstatistik konnte für diese spektral resonant gekoppelten Quantenpunkt-Mikroresonatorsysteme sowohl unter kontinuierlicher- als auch unter gepulst-elektrischer Anregung Einzelphotonen-Emission nachgewiesen werden. […] Anhand einer eingehenden Analyse der Emissionsraten sowie der elektrischen Injektionseffizienzen bei Anregungs-Repetitionsraten von bis zu 220 MHz konnte gezeigt werden, dass die untersuchten Mikroresonatoren zudem als äußerst effiziente, elektrisch getriggerte Einzelphotonenquellen eingesetzt werden können. Sowohl bezüglich der Einzelphotonen-Emissionsraten von bis zu (47,0+/-6,9) MHz als auch der Gesamteffizienz der Bauteile bis hin zu (34+/-7) % konnten dabei Rekordwerte erzielt werden. Korrelierte Photonenpaare elektrisch gepumpter Quantenpunkte: […] Quanten-Schlüsselverteilung mit elektrisch getriggerten Einzelphotonenquellen: Ausgehend von den grundlegenden Untersuchungen dieser Arbeit, erfolgte die erstmalige Implementierung elektrisch getriggerter Quantenpunkt-Einzelphotonenquellen in Experimenten zur Quanten-Schlüsselverteilung. Basierend auf den eingehend analysierten Quantenpunkt-Mikroresonatoren, wurden dabei zwei Experimente in Freistrahloptik mit unterschiedlichen Übertragungsdistanzen durchgeführt. In beiden Fällen wurde ein BB84-Protokoll nachgeahmt, indem auf die einzelnen Photonen eine feststehende Abfolge von vier unterschiedlichen Polarisationszuständen aufmoduliert wurde. Das erste Experiment, durchgeführt im Labormaßstab in Würzburg, basierte auf einem Quantenkanal mit einer Länge von etwa 40 cm und arbeitete bei einer Taktrate von 183 MHz. Die höchste dabei erzielte ausgesiebte Schlüsselrate (engl. sifted-key rate) betrug 35,4 kbit/s bei einem Quanten-Bitfehlerverhältnis (QBER) von 3,8 %. Der Einzelphotonen-Charakter der Emission innerhalb des Quantenkanals konnte jeweils eindeutig nachgewiesen werden […]. Das zweite Experiment zur Quanten-Schlüsselverteilung wurde mittels zweier Teleskope über eine Distanz von 500 m in der Münchner Innenstadt zwischen den Dächern zweier Gebäude der Ludwig-Maximilians-Universität realisiert. […] Bei einer Taktrate von 125 MHz konnte mit diesem System im Einzelphotonen-Regime eine maximale sifted-key rate von 11,6 kbit/s bei einem QBER von 6,2 % erzielt werden. Diese erstmalige Implementierung elektrisch betriebener, nicht-klassischer Lichtquellen in Experimenten zur Quanten-Schlüsselverteilung stellt einen wichtigen Schritt hinsichtlich der Realisierung effizienter und praktikabler Systeme für die Quantenkommunikation dar. / Quantum key distribution is the first commercially available technology of quantum information and allows for secure data communication by utilizing single-photons or entangled photon-pairs for key generation. The required non-classical light states can be produced by semiconductor quantum dots. Compared to other quantum emitters, such as isolated atoms, organic molecules or vacancy centers in diamond nanocrystals, they offer the advantage of being capable for the integration into complex semiconductor microstructures. Therefore quantum dots are predestinated for the development of novel optoelectronic devices on a scalable technology platform. In this context, the work at hand explores the properties of electrically-pumped quantum dot microstructures. Thereby selforganized InAs/GaAs quantum dots serve as optically active medium. Aim of this work is the generation of non-classical light for applications in quantum communication, at which the study focuses specifically on electrical operation of the respective quantum light sources. In this framework pronounced cavity effects in the weak coupling regime of light-matter interaction will be employed to realize bright single-photon sources. Furthermore the properties of correlated photon-pairs from two spectrally-seperated quantum dot states will be analyzed. The structures were investigated by means of microluminescence spectroscopy with high spatial and temporal resolution. Moreover, experiments on the photon statistics were performed by measurements of the second-order auto- and cross-correlationfunction. As specified below, achievements within this study range from fundamental investigations on quantum dot microstructures to the first implementation of electrically-triggered quantum dot single-photon sources in realistic quantum key distribution experiments outside a shielded lab environment. Electrically-Triggered Single-Photon Sources: For the generation of electrically-triggered single-photons quantum dots were embedded in microcavities. The latter ones are based on doped Fabry-Pérot micropillar resonators featuring a design that was optimized for enhanced photon-exctraction effiency. […] Photon statistic measurements on these resonantly-coupled quantum dot micropillar systems prooved single-photon emission under continuous electrical as well as pulsed electrical excitation. […] A detailed investigation of the photon emission rates and carrier injection efficincies at excitation repetition rates of up to 220 MHz showed, that the micropillar cavities can be used as extremely efficient single-photon sources. Record high values for single-photon emission rates of up to (47.0+/-6.9) MHz as well as overall efficiencies of up to (34+/-7) % were achieved for these devices. Correlated Photon-Pairs of Electrically Pumped Quantum Dots: […] Quantum Key Distribution Using Electrically Triggered Single-Photon Sources: Based on the fundamental investigations in this work, the first implementation of electrically driven quantum dot single-photon sources into quantum key distribution experiments was carried out. Utilizing the investigated quantum dot micropillar cavities, two free space experiments were performed with different transmission distances. In both cases a BB84-protocoll was emulated by modulating the single-photons with a fixed pattern of four different polarization settings. The first experiment, performed on a lab-scale in Würzburg, is based on a 40 cm quantum channel and worked at a clock rate of 183 MHz. Sifted-key rates of up to 35.4 kbit/s with a quantum bit error ratio (QBER) of 3.8 % were achieved. Single-photon emission within the quantum channel was proven unambiguously […]. The second quantum key distribution experiment was realized over a distance of 500 m in downtown Munich, connecting two buildings of the Ludwig-Maximilians-Universität via telescopes on the rooftops. […] Using this system at a clock rate of 125 MHz, a maximum sifted-key rate of 11.6 kbit/s at a QBER of 6.2 % was achieved in the single-photon regime. This first implementation of an electrically-driven non-classical light source in quantum key distribution experiments can be considered as a major step toward the realization of efficient and practical quantum communication systems.

In this thesis two main projects are presented, both aiming at the overall goal of particle detector development. In the first part of the thesis detailed shielding studies are discussed, focused on the shielding section of the planned New Small Wheel as part of the ATLAS detector upgrade. Those studies supported the discussions within the upgrade community and decisions made on the final design of the New Small Wheel. The second part of the thesis covers the design, construction and functional demonstration of a test facility for gaseous detectors at the University of Würzburg. Additional studies on the trigger system of the facility are presented. Especially the precision and reliability of reference timing signals were investigated. / In dieser Arbeit werden zwei Projekte vorgestellt, welche beide das gemeinsame Ziel der Entwicklung von Teilchendetektoren verfolgen. Im ersten Teil der Arbeit werden ausführliche Simulationsstudien zur Abschirmung behandelt, die sich auf die Abschirmungsbereiche des geplanten New Small Wheels als Teil der ATLAS-Detektor Verbesserungen konzentrieren. Diese Studien unterstützten die Diskussionen innerhalb der Upgrade-Gemeinschaft und Entscheidungen, welche für die endgültige Kostruktionsplanung des New Small Wheels getroffen wurden. Der zweite Teil der Arbeit umfasst die Konstruktion, den Aufbau sowie den Funktionsnachweis eines Teststandes für Gasdetektoren an der Universität Würzburg. Ebenfalls werden Studien über das Triggersystems des Teststandes dargestellt. Insbesondere wurden die Präzision und Verlässlichkeit von Referenzzeitsignalen untersucht.

Bruce R. Musicus. / Cover title.

Outstanding scientific results and statistical overview of the Institute of Ion Beam Physics and Materials Research in 2008

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Nature abounds with ingenious nanoscopic machines employed to carry out all of the requisite tasks that collectively contribute to the molecular basis of life. This thesis focuses primarily on a sub-set known as "molecular walkers" which can perambulate along intracellular molecular motorways carrying out such essential tasks as vesicle transport and muscle contraction. A summary of these incredible natural motors is presented in Chapter I along with a review of the artificial small-molecule mimics reported to date. When elucidating a set of design principles for synthetic analogues, inspiration is taken from the mechanism of the biological bipedal motor protein kinesin with a focus on potential strategies to enable directional walking. Transition metal-ligand chemistry is utilised as one such strategy in Chapter II through the governance of walker-track interactions in the design, synthesis and operation of a bimetallic molecular biped. A palladium(II) moiety is selectively and intramolecularly stepped between pyridine-derivative binding sites in the track using a thermal stimulus in the presence of a coordinating solvent. Acid-base manipulations facilitate directional stepping by means of an energy ratchet mechanism allowing the track to do work on the biped unit and ultimately drive it away from equilibrium. The potential of malleable transition metal binding-event energetics is explored further in Chapter III with the design and synthesis of a platinum(II)-complexed [2]rotaxane. Thermodynamic and kinetic stimuli are investigated as means to mediate selective shuttling of a Pt-complexed macrocycle between two ligand binding sites in the thread. The substitution pattern of the ligands and the kinetic stability of the metal-ligand bonds afford exceptional metastability to the co-conformers of the molecule in the absence of an external stimulus providing the possibility for long-term information storage. In Chapter IV, a novel macrocycle is used to demonstrate the chemical orthogonality of acid-mediated hydrazone exchange with respect to the palladium(II) stepping mechanism described in Chapter II and show that two such motifs can be independently addressed within a single molecule. These linkages are then utilised as mutually exclusive chemo-selective switches to individually operate opposing feet in an unprecedented first-generation small-molecule walker-track system.

No description available.

An Optima 3000 ICP-AES instrument was modified and the equipment necessary to carry out axial excitation atomic fluorescence was designed and constructed. Using this calibrated system, preliminary fluorescence experiments were not successful. As fluorescence is proportional to source intensity, it was considered that the excitation source, a hollow cathode lamp, may not have been sufficiently intense to produce fluorescence. A novel excitation source-driver system was designed and built in-house to operate HCLs, BDHCLs and LEDs with variable modulation frequencies and duty cycle capabilities. Studies investigating lamp response to changes in modulation frequency and duty cycle indicated that a lamp operated with a lower modulation frequency range (167 - 542 Hz) and higher duty cycles (30 - 50 %) should provide the preferred intense excitation conditions for the production of fluorescence in the ICP, When a Thermo Elemental PQ2 instrument was used, fluorescence was obtained immediately. Um'variate searches were used to optimise several plasma parameters, i.e. forward power; viewing height ALC; plasma, nebuliser and auxiliary gas flow rates. Once the optimum conditions had been determined, calibration curves were plotted for each of the elements studied (Ba, Li, Mg and Na). The calibration showed excellent linearity over five orders of magnitude (R? values ranged from 0.99995 to 1.0000) and the precision on each data point was better than 5 % RSD. Limits of detection were determined to be 27.6, 0.51, 0.43 and 0.20 ug 1* for Ba, L i , Mg and Na, respectively, which approached those reported in the literature for a commercial system. Vertical profiles of the plasma, using radial excitation, were obtained for Ba, Li , Mg and Na. Using the optimum conditions for Li and Na, vertical profiles of the plasma, using axial excitation with the more intense LEDs, were obtained. Both profiles showed that there was a relatively sharp optimum, with respect to fluorescence signal, as a function of viewing height ALC. The optimum viewing heights ALC obtained, for both radial and axial excitation fluorescence, were identical, suggesting that, irrespective of the excitation arrangement employed, only particular conditions produced in the plasma give the optimum conditions for fluorescence and that these are spatially dependent. Plasma diagnostics were performed in an attempt to explain why fluorescence was observed using the plasma produced by the Thermo Elemental but not by the Optima 3000 generator. At a viewing height of 50 mm ALC, Texc and Trot were 3080 and 2500 K for plasmas produced using the Thermo Elemental generator and 3600 and 2830 K for the Optima 3000 generator, respectively. Temperatures were calculated using the mean emission intensity at particular wavelengths. The intensities of the emitting species from the Thermo Elemental ICP were lower than those obtained from the Optima 3000 ICP for supposedly 'identical' conditions. If the number of excited species gives rise to lower emission intensities, then there must be more atoms in the lower/ground state from the plasma produced using the Thermo Elemental generator. This is of vital importance because for fluorescence to occur the fluorescence emission intensity will be dependent on the number available in the ground state for excitation {i.e. a relatively 'cool' plasma is required for fluorescence to occur). As very similar plasma operating conditions and the same concentration solutions were used in the fluorescence experiments performed using both the Optima 3000 and the Thermo Elemental ICPs, the differences observed in plasma performance may be attributed to efficiency of coupling of the generators used.