Stuttgart, Univ., Diss., 2002.

Universiẗat, Diss., 2002--Bonn.

Universiẗat, Diss., 2003--Bonn.

Universiẗat, Diss., 2005--Bonn.

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.

This dissertation explores the ethnic and religious dimensions of the northern Nigeria conflict in which gruesome killings have intermittently occurred, to determine whether there are genocidal inclinations to the episodic killings. The literature review provides the contextual framework for examining the conflict parties and causation factors to address the research questions: Are there genocidal inclinations to the ethno-religious conflict in northern Nigeria? To what extent does the interplay between ethnicity and religion help to foment and escalate the conflict in northern Nigeria? The study employs a mixed content analysis and grounded theory methodology based on the Strauss and Corbin (1990) approach. Data sourcing was from 197 newspaper articles on the conflict over the study period spanning from the 1966 northern Nigeria massacres of thousands of Ibos up to present, ongoing killings between Muslims and Christians or non-Muslims in the region. Available texts of the conflict cases over the research period were content-analyzed using Nvivo qualitative data analysis software involving processes of categorizing, coding and evaluation of the textual themes. The study structures a theoretical model for determining proclivity to genocide, and finds that there are genocidal inclinations to the northern Nigeria conflict, involving the specific intent to ‘cleanse’ the north through the exclusionary ideology of imposition of the Sharia law through enforced assimilation or extermination of Christians and other non-Muslims who do not assimilate or adopt the Muslim ideology. The study also suggests that there is latency in the recognition of these genocidal manifestations due to their episodic nature and intermittency of occurrence. he study provides further understanding of factors underlying and sustaining the violent conflict between Muslims and Christians in northern Nigeria. It contributes new perspectives and theoretical model for determining genocidal proclivity to the field of conflict analysis and resolution, and proffers alternative strategies for relationship building and peaceful coexistence among different religious groups. The findings will guide recommendations on policy formulations for eliminating religious intolerance in northern Nigeria. The study creates further awareness on the need for global intervention on the region’s sporadic killings to avert full blown Rwandan type genocide in Nigeria.