abstract: A series of experiments using a polarized beam incident on a polarized frozen spin target (FROST) was conducted at Jefferson Lab in 2010. Results presented here were taken during the second running period with the FROST target using the CEBAF Large Acceptance Spectrometer (CLAS) detector at Jefferson Lab, which used transversely-polarized protons in a butanol target and a circularly-polarized incident tagged photon beam with energies between 0.62 and 2.93 GeV. Data are presented for the F and T polarization observables for h meson photoproduction on the proton from W = 1.55 GeV to 1.80 GeV. The data presented here will improve the world database and refine theoretical approaches of nucleon structure. / Dissertation/Thesis / Doctoral Dissertation Physics 2016

The GlueX experiment aims to study meson photoproduction while utilizing the coherent bremsstrahlung technique to produce a 9 GeV linearly polarized photon beam incident on a liquid $\mathrm{H_{2}}$ target. A Start Counter detector was fabricated to properly identify the accelerator electron beam buckets and to provide accurate timing information. The Start Counter detector was designed to operate at photon intensities of up to $\mathrm{10^{8}\gamma/s}$ in the coherent peak and provides a timing resolution $\mathrm{\sim 300\ ps}$ so as to provide successful identification of the electron beam buckets to within 99\% accuracy. Furthermore, the Start Counter detector provides excellent solid angle coverage, $\sim 90 \%\ \mathrm{of}\ 4 \pi\ \mathrm{hermeticity}$, and a high degree of segmentation for background rejection. It consists of a cylindrical array of 30 scintillators with pointed ends that bend towards the beam at the downstream end. Magnetic field insensitive silicon photomultiplier detectors were selected as the readout system. An initial measurement of the beam asymmetry $\Sigma$ in the exclusive reaction $\vec{\gamma}p \rightarrow \pi^{0}p$, where $\pi^{0} \rightarrow \gamma \gamma$ has been carried out utilizing the GlueX spectrometer during the Spring 2015 commissioning run. The tagged photon energies ranged from $2.5 \leq E_{\gamma} \leq 3.0\ \mathrm{GeV}$ in the coherent peak. These measurements were then compared to the world data set and show remarkable agreement with only two hours of physics production running.

The diffractive open charm production is studied using data from 2006-2007, when the leading proton measurement by H1 Very Forward Proton Spectrometer was provided. The charm production is tagged by the decay products of D∗ meson. The cross section of e+ p → e+ D∗ X p in photoproduction regime defined by the value of virtuality Q2 < 2 GeV is determined and corrected for the detector effects. The diffractive D∗ meson photoproduction cross section is compared with the hadron level MC Rapgap prediction based on diffractive parton distribution functions extracted from inclusive ep DIS measurements. Measurement of leading proton provides a unique opportunity to investigate the response of forward detectors for the diffractive events. Using such events, the performance of the large rapidity gap selection is examined.

The cross section of the diffractive process e+p → e+Xp is measured at a centre-of-mass energies of 319 GeV, where the system X contains at least two jets and the leading final state proton p is detected in the H1 Very Forward Proton Spectrometer. The measurement is performed in photoproduction defined by photon virtualities Q2 < 2 GeV2 and in deep-inelastic scattering with 4 GeV2 < Q2 < 80 GeV2 . The results are compared to next-to-leading order QCD calculations based on diffractive parton distribution functions as extracted from measurements of inclusive cross sections in diffractive deep- inelastic scattering. A collinear QCD factorization theorem is tested against the measured cross sections and their ratios. 1

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京都大学 / 0048 / 新制・論文博士 / 博士(理学) / 乙第13217号 / 論理博第1562号 / 新制||理||1638(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 永江 知文, 教授 鶴 剛, 准教授 成木 恵 / 学位規則第4条第2項該当 / Doctor of Science / Kyoto University / DFAM

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Les microorganismes photosynthétiques suscitent un intérêt biotechnologique grandissant pour la production de dihydrogène (H₂) à partir d'eau et d'énergie solaire en préservant l'eau douce et les terres cultivables sans ajout d'engrais. La cyanobactérie modèle Synechocystis PCC 6803 est capable de produire du H₂ de manière faible et transitoire grâce à une hydrogénase [NiFe] bidirectionnelle Hox. Cette enzyme possède 5 sous-unités protéiques (HoxEFUYH) qui catalysent la réaction réversible : 2H⁺ + 2e⁻ ↔ H₂. Le site actif [NiFe] de cette enzyme est assemblé par un complexe de six protéines HypABCDEF. L’hydrogénase est ensuite maturée par une protéase HoxW qui clive la sous-unité HoxH et active le site catalytique [NiFe]. L’ingénierie de cyanobactéries pour la photoproduction biologique d’H₂ passe par une meilleure compréhension du rôle de l'hydrogénase dans le métabolisme cyanobactérien. Au cours de ma thèse, j’ai construit et analysé 7 mutants sophistiqués de Synechocystis permettant la surexpression simultanée (constitutive ou régulée par la température de croissance) des gènes hoxEFUYHW et hypABCDEF. On a ainsi montré que la surproduction simultanée des protéines HoxEFUYHW et HypABCDEF combinée à une augmentation de la disponibilité de nickel dans le milieu conduit à une augmentation de l’activité hydrogénase d’un facteur 20. D’autre part, un mutant dépourvu de l'opéron hoxEFUYH a permis également de montrer que l'hydrogénase n'est pas indispensable à la croissance dans les conditions photoautotrophiques standard. La comparaison des phénotypes des divers mutants construits durant ce travail a permis également de montrer pour la première fois que l’hydrogénase joue un rôle dans la défense cellulaire contre le stress oxydant induit par le H₂O₂, par la présence de glucose ou de glycérol dans le milieu de culture. Par ailleurs, j'ai participé à la caractérisation d'un nouveau régulateur de l'expression de l’hydrogénase. Ce facteur de transcription (AbrB2) qui réprime l’opéron hoxEFUYH est impliqué dans la tolérance au stress induit par le diamide ou le nickel. Un contrôle redox de l'activité de ce régulateur par une modification post-traductionnelle de glutathionylation a été mise en évidence pour la première fois chez les cyanobactéries. L'ensemble de ces résultats démontre que l’on doit combiner plusieurs stratégies génétiques et physiologiques pour augmenter fortement la production d’hydrogène chez Synechocystis, et que nos mutants sont des outils très importants vers cet objectif. / Photosynthetic organisms are attractive organisms for hydrogen production using water and solar energy, while preserving fresh water and arable soils without adding fertilizers. The model cyanobacterium Synechocystis PCC 6803 produces small and transitory amounts of H₂ thanks to its bidirectional [NiFe] hydrogenase Hox. The Hox complex with its 5 protein subunits (HoxEFUYH) catalyzes the reversible reaction 2H⁺ + 2e⁻ ↔ H₂. The [NiFe] catalytic site of the Hox enzyme is assembled using a six-subunits HypABCDEF complex and matured by the HoxW protease that cleaves HoxH and activates its [NiFe]-containing center. Engineering cyanobacteria for hydrogen production relies on a better understanding of the role of hydrogenase in the cyanobacterium metabolism. During my PhD, I have constructed and analyzed 7 sophisticated mutants of Synechocystis, allowing the simultaneous over-expression (constitutive or regulated by the growth temperature) of the hoxEFUYH and hypABCDEF genes. We demonstrated that the simultaneous over-production of the HoxEFUYH and HypABCDEF proteins, combined to an increase in nickel availability led to an approximately 20-fold increase of the active hydrogenase level. Moreover, using a deleted hox-operon mutant we showed that hydrogenase is dispensable in standard phototrophic growth conditions. Comparing the phenotypes of different mutants constructed in this study enables us to demonstrate for the first time that the hydrogenase operates in cell protection against oxidative stress (H₂O₂) and sugar stress (glucose or glycerol). Besides, I have also participated to the characterization of a new regulator (AbrB2) of the expression of the hydrogenase. This transcription factor represses the hoxEFUYH operon and is involved in the tolerance to stress induced by diamide or nickel. For the first time in cyanobacteria, a redox control of the activity of this regulator by a post-translational gluthathionylation was identified. Collectively, our findings showed that several genetic and physiological strategies should be combined in a single strain to strongly increase hydrogen production in Synechocystis. Meanwhile the presently constructed mutants proved to be very powerful tools to achieve this goal.