Stuttgart, Univ., Diss., 2002.

Universiẗat, Diss., 2002--Bonn.

Universiẗat, Diss., 2003--Bonn.

Universiẗat, Diss., 2005--Bonn.

Diese Dissertation führt einen umfassend modular aufgebauten digitalen Zwilling der Positronen-Annihilation-Lebensdauerspektroskopie (PALS) ein, der das Ziel verfolgt, ein tiefergehendes Verständnis der Messmethode zu ermöglichen und aufzuzeigen, wie die Konfiguration des experimentellen Setups sowie die Eigenschaften der verwendeten radioaktiven Positronenquelle zu Verzerrungen im Lebensdauerspektrum führen können. Aufgrund der mathematischen Komplexität realer Lebensdauerspektren, die eine Zerlegung in ihre Komponenten erschwert, und der Herausforderung, die Instrumentauflösungsfunktion / engl.: Instrument Response Function (IRF) genau zu bestimmen, bietet der digitale Zwilling eine innovative Lösung, um jegliche Fragen zur Hardware der PALS mittels einer realitätsgetreuen digitalen Nachbildung des gewünschten Setups zu beantworten. Der entwickelte digitale Zwilling setzt sich aus drei Kernmodulen zusammen, die schrittweise tiefergehende Einblicke in das simulierte Setup und schließlich in das resultierende Lebensdauerspektrum bieten. Im ersten Modul wird die Open-Source-Softwareplattform Geant4 genutzt, um die physische Welt in eine digitale Umgebung zu überführen. Hierbei steht die Modellierung von Teilcheninteraktionen mit Materie im Fokus, die durch die flexible Architektur von Geant4 ermöglicht wird. In diesem Kontext wurde eine spezifische Simulation implementiert, die eine differenzierte Betrachtung der Gamma-Quanten-Energien erlaubt und somit ein präziseres Verständnis der PALS-Methodik ermöglicht. Im zweiten Modul erfolgt die Kopplung der aus Geant4 gewonnenen Daten-Streams mit dem DLTPulseGenerator über eine speziell entwickelte Schnittstelle. Diese Schnittstelle bietet neben der sequenziellen Verarbeitung der Daten-Streams die Einbindung physikalischer Prozesse wie der Positronen-Lebensdauer, sowie die Quellstärke des als Positronenstrahler verwendeten radioaktiven Isotops und der zeitlichen Unschärfe des Photo-Multipliers / engl.: Photo-Multiplier-Tube (PMT), wodurch eine umfassende Untersuchung verschiedener Effekte mit einem einzigen Datensatz möglich wird. Dies führt zu einer hohen Vergleichbarkeit der Ergebnisse. Darüber hinaus ermöglicht die Schnittstelle eine detaillierte Klassifizierung möglicher Ereignisse innerhalb der PALS-Methode, was es ermöglicht, quantitative Effekte spezifischer Ereignisse zu untersuchen. Dabei gibt die Schnittstelle sowohl wichtige Informationen aus der Geant4-Simulation als auch Informationen aus ihren eigenen Funktionen an den DLTPulseGenerator weiter, welcher digitalisierte PMT Output-Pulse je nach gewählter Konfiguration des gewählten Digitizers erzeugt. Das dritte Modul nutzt die DDRS4PALS Software zur Analyse des aus dem zweiten Modul stammenden Daten-Streams, um Informationen über das Lebensdauerspektrum zu extrahieren. Hierbei wird erstmals die Validierung physikalischer Filter am Gesamtspektrum und seiner Anteile gewährt, da durch die Klassifizierung im zweiten Modul des digitalen Zwillings ermöglicht wird, lediglich die unerwünschten Anteile im Lebensdauerspektrum zu betrachten und somit die tatsächliche Wirkung der physikalischen Filter auf diese zu untersuchen. Der modular und flexibel gestaltete digitale Zwilling der PALS ermöglicht eine einfache Anpassung an veränderte experimentelle Setups und kann auch für ähnliche Messmethoden (z.B. Fluoreszenz-Lebensdauer-Spektroskopie) adaptiert werden. Dadurch markiert der digitale Zwilling einen signifikanten Fortschritt in Richtung einer digitalen Ära der Forschung und trägt zu einem verbesserten Verständnis der Messmethode sowie zu effizienteren und kostengünstigeren Optimierungsprozessen bei. / This dissertation introduces a comprehensively modular digital twin of Positron Annihilation Lifetime Spectroscopy (PALS), aimed at enabling a deeper understanding of the measurement method and demonstrating how the configuration of the experimental setup and the properties of the used radioactive positron source can lead to distortions in the lifetime spectrum. Due to the mathematical complexity of real lifetime spectra, which complicates their decomposition into components, and the challenge of accurately determining the Instrument Response Function (IRF), the digital twin offers an innovative solution to address any hardware-related questions of PALS by using a realistic digital replication of the desired setup. The developed digital twin comprises three core modules that provide progressively deeper insights into the simulated setup and ultimately the resulting lifetime spectrum. The first module utilizes the open-source software platform Geant4 to transform the physical world into a digital environment. Here, the focus is on modelling particle interactions with matter across a broad energy spectrum, including electromagnetic processes, facilitated by Geant4's flexible architecture. Within this context, a specific simulation was implemented, allowing a detailed examination of gamma quantum energies, thus enabling a more precise understanding of the PALS methodology. The second module involves coupling the data streams generated by the Geant4-Simulation with the DLTPulseGenerator via a specially developed interface. This interface, in addition to sequential processing of data streams, incorporates physical processes such as the positron lifetime, the source strength of the radioactive isotope used as a positron emitter, and the temporal uncertainty of Photo-Multiplier-Tubes (PMTs), thereby enabling a comprehensive examination of various effects with a single dataset. This leads to high comparability of results. Moreover, the interface facilitates a detailed classification of potential events within the PALS method, allowing for quantitative investigations of specific event effects. The interface conveys both critical information from the Geant4-Simulation and its functions to the DLTPulseGenerator, which generates digitized PMT output pulses based on the chosen configuration of the digitizer. The third module utilizes the DDRS4PALS software to analyse the data stream generated by the second module, extracting information about the lifetime spectrum. This approach allows for the first-time validation of physical filters on the overall spectrum and its components. By classifying data in the second module of the digital twin, it becomes possible to focus solely on the undesired components within the lifetime spectrum. This enables a precise investigation of the actual impact of physical filters on these components. The modular and flexible design of the digital twin allows for easy adaptation to altered experimental setups and can also be adjusted for similar measurement methods (e.g. Fluorescence Lifetime Spectroscopy). Thus, the digital twin signifies a significant step towards a digital era of research, contributing to an enhanced understanding of the measurement method and more efficient and cost-effective optimization processes.

Stuttgart, Univ., Diss., 2003.

Universiẗat, Diss., 2003--Stuttgart.

<p>This thesis treats the mass range of charmonium states and excited gluonic fields in two experiments, BESII and PANDA, and outlines a phenomenological model that connects them.</p><p>In BESII, <i>e</i>⁺<i>e</i>^– form a charmonium initial state, which is utilised as a source for secondary particles. The analysed channels, <i>ψ</i>´→ <i>γK</i>⁺<i>K</i>^– and <i>ψ</i>´→ <i>γπ</i>⁺<i>π</i>^–, give access to intermediate scalar states such as the two glueball candidates: f₀(1500) and f₀(1710). The f₀(1710) is indeed observed in decay into both <i>π</i>⁺<i>π</i>^– and <i>K</i>⁺<i>K</i>^– and the f₀(1500) is accepted as a necessary part of the <i>π</i>⁺<i>π</i>^– signal at the moderate 5% level. In addition, we observe the two tensor states f₂(1270) (in both channels) and f₂´(1525) (in <i>K</i>⁺<i>K</i>^–), but the need for the f₂´(1525) is not firmly established. The region around 2 GeV/<i>c</i>² is fitted with an f₄(2050) and an f₀(2200) in <i>π</i>⁺<i>π</i>^–. This region is fairly flat in <i>K</i>⁺<i>K</i>^– with a slight peak at the f₀(2200). Branching ratios for all eight channels are given. A fit to the angular distribution of ψ´→ γ f₂(1270) → <i>γ π</i>⁺<i>π</i>^–gave two possible solutions for the relative importance of helicity projections zero, one and two.</p><p>The future <i>pp</i>bar experiment PANDA is still in the development phase; important physics goals have been defined and we are now taking on the laborious task of constructing a detector that is able to fulfil them. A simulation investigation of a theoretically preferred <i>J</i><i>PC</i>=1^–+ charmonium hybrid (<i>H</i><i>c</i>) is presented: <i>ppbar</i> → <i>H</i><i>c</i><i>π</i>⁰/<i>η</i>, <i>H</i><i>c</i> → <i>χ</i><i>c</i>₁ (<i>π</i>⁰<i>π</i>⁰)<i>S–wave</i>, <i>χ</i><i>c</i>₁ → <i>J</i>/<i>ψπ</i>⁰, with a final state of seven photons and a lepton pair. To detect this channel next to full coverage of CM phase space is needed and as little material as possible before the electromagnetic calorimeter. </p><p>A second simulation study of <i>pp</i>bar → <i>η</i><i>c</i> → <i>γγ</i> at PANDA, suggests that the channel should be possible to detect with a signal-to-background ratio of 5±1 and a detection efficiency of at least 10%. </p><p>By assuming a constant matrix element we obtain a relation between the decay width for <i>ψ</i> → <i>pp</i>bar+<i>m</i>, which has been measured at BES for several cases, and the cross section for <i>pp</i>bar charmonium production in association with the same light meson, <i>m</i> (at for example PANDA). Cross sections of ~300–3000 pb were predicted for J/ψ production and ~30 pb for <i>ψ</i>' production. Isoscalars seem to be preferred to isovectors in <i>J</i>/<i>ψ</i> production, this might however be an artefact of simplifications within the model. A comparison with the only measured cross section, <i>pp</i>bar → <i>J</i>/<i>ψπ</i>⁰, suggests that the model is useful as a first estimate.</p>

This thesis treats the mass range of charmonium states and excited gluonic fields in two experiments, BESII and PANDA, and outlines a phenomenological model that connects them. In BESII, e+e– form a charmonium initial state, which is utilised as a source for secondary particles. The analysed channels, ψ´→ γK+K– and ψ´→ γπ+π–, give access to intermediate scalar states such as the two glueball candidates: f0(1500) and f0(1710). The f0(1710) is indeed observed in decay into both π+π– and K+K– and the f0(1500) is accepted as a necessary part of the π+π– signal at the moderate 5% level. In addition, we observe the two tensor states f2(1270) (in both channels) and f2´(1525) (in K+K–), but the need for the f2´(1525) is not firmly established. The region around 2 GeV/c2 is fitted with an f4(2050) and an f0(2200) in π+π–. This region is fairly flat in K+K– with a slight peak at the f0(2200). Branching ratios for all eight channels are given. A fit to the angular distribution of ψ´→ γ f2(1270) → γ π+π–gave two possible solutions for the relative importance of helicity projections zero, one and two. The future ppbar experiment PANDA is still in the development phase; important physics goals have been defined and we are now taking on the laborious task of constructing a detector that is able to fulfil them. A simulation investigation of a theoretically preferred JPC=1–+ charmonium hybrid (Hc) is presented: ppbar → Hcπ0/η, Hc → χc1 (π0π0)S–wave, χc1 → J/ψπ0, with a final state of seven photons and a lepton pair. To detect this channel next to full coverage of CM phase space is needed and as little material as possible before the electromagnetic calorimeter. A second simulation study of ppbar → ηc → γγ at PANDA, suggests that the channel should be possible to detect with a signal-to-background ratio of 5±1 and a detection efficiency of at least 10%. By assuming a constant matrix element we obtain a relation between the decay width for ψ → ppbar+m, which has been measured at BES for several cases, and the cross section for ppbar charmonium production in association with the same light meson, m (at for example PANDA). Cross sections of ~300–3000 pb were predicted for J/ψ production and ~30 pb for ψ' production. Isoscalars seem to be preferred to isovectors in J/ψ production, this might however be an artefact of simplifications within the model. A comparison with the only measured cross section, ppbar → J/ψπ0, suggests that the model is useful as a first estimate.

De nouveaux nano-objets anisotropes fluorescents sont obtenus par l’assemblage d’acènes spécifiquement conçus. Dans des cristaux, nano-rubans et nanoparticules anisotropes de 2,3-dialkyldiphenylanthracènes, les efficacités et la polarisation de l’émission bleue sont remarquables. La couleur de l’émission est accordée par le dopage avec des émetteurs verts et oranges (di- et tétra-phényltétracènes). La microscopie confocale de fluorescence permet d’étudier les cinétiques des états excités et des transferts d’énergie photo-induits, ainsi que la dispersion et les orientations des émetteurs. Pour la première fois, l’influence de la largeur de nano-rubans sur la cinétique d’annihilations triplet-triplet de tétracènes est mise en évidence. La microscopie révèle également le polymorphisme inhabituel d’un dérivé diéthynylphényl-anthracène. Ce travail ouvre des perspectives pour le développement et l’étude de processus fondamentaux de nano-matériaux luminescents. / New fluorescent anisotropic nano-objects are obtained by the assembly of specifically designed acenes. In crystals, nano-ribbons and anisotropic nanoparticles of 2,3-dialkyldiphenylanthracenes, the efficiencies and the polarization of the blue emission is remarkable. The color of the emission is tuned by doping with green and orange emitters (di-and tetra-phenyltetracenes). Confocal fluorescence microscopy is used to study the kinetics of excited states and photo-induced energy transfers, as well as the dispersion and orientation of the emitters. For the first time, the influence of the width of the nano-ribbons on the kinetics of tetracene triplet-triplet annihilations is highlighted. Microscopy also reveals the unusual polymorphism of a diethynylphenyl anthracene derivative. This work opens perspectives for the development and study of fundamental processes of luminescent nano-materials.