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.

Presented in this thesis are measurements of W boson production in high energy pp collisions and ep deep inelastic scattering that take place at RHIC and HERA facilities, respectively. These measurements explore the inner structure of the nucleons, in particular, probing the distributions of the light flavor sea which consists of up, down and strange quarks. The W+/W− cross-section ratio, RW , in pp collisions is sensitive to the asymmetry in the ¯d and ¯u flavors in the nucleon sea. This ratio was first measured with the STAR detector at RHIC with the data collected in 2009 and again with the data collected from 2011 to 2013, featuring pp collisions of a center-of-mass energy of √s = 500/510 GeV and an integrated luminosity of ∼ 350 pb−1. The study considered in this thesis further improves the precision of this measurement by analyzing an additional data set collected in 2017 which corresponds to an integrated luminosity of ∼ 350 pb−1. The experimental results are compared to theory predictions generated with various global PDF fits. The measurement performed at HERA searches for the strange quark content in the nucleon via charm production in charged current deep inelastic scattering. This is the first measurement of its kind, using the HERA II data collected with the ZEUS detector. This data set corresponds to e±p collisions at a center-of-mass energy of √s = 318 GeV with an integrated luminosity of 358 pb−1. The results are consistent with expectations from the Standard Model, albeit with large experimental uncertainties arising from the limited statistics. / Physics

In dieser Arbeit wird ein erster Versuch vorgestellt, die inklusive Produktion von neutralen Pionen durch ihren Zerfall in zwei Photonen zu messen. Dazu wurde der HERA-B Detektor in der Konfiguration des Frühjahrs `99 benutzt. Für die Bestimmung des Produktionsquerschnittes der neutralen Pionen werden die Daten aus dem inneren Bereich des elektromagnetischen Kalorimeters verwendet. Die Messung wurde mit zwei verschiedenen Target-Materialien, Kohlenstoff und Titan, durchgeführt. Aus diesem wird die Materialabhängigkeit der Pionen-Produktion ermittelt. Mehrere Methoden zur Bestimmung der Luminosität bei HERA-B werden untersucht. Es wird gezeigt, dass die durchschnittliche Anzahl von Wechselwirkungen mit Hilfe der im elektromagnetischen Kalorimeter deponierten Energie gemessen werden kann. Diese Methode bietet eine Möglichkeit zur Luminositätsbestimmung mit hoher Genauigkeit. Die Durchführbarkeit, die hadronische Produktion von Leptonpaaren in hohen Massenbereichen mit HERA-B zu messen, wird in Monte-Carlo-Simulationen untersucht. Diese zeigen, dass die erwartete Massenauflösung eine Beobachtung des Ypsilon-Signals über dem Untergrund und eine Trennung der Zustände Ypsilon (1S) und Ypsilon (2S) erlaubt. Es wird gezeigt, dass eine genaue Messung der Ypsilon-Polarisation möglich ist. Diese Messung bietet eine sehr gute Möglichkeit, die verschiedenen Mechanismen für die Produktion schwerer Quarkonium-Zustände zu testen. / A first attempt to measure the cross section of inclusive production of neutral pions decaying into two photons using the HERA-B detector in the spring of '99 configuration is presented. The pions cross section is determined using data from the inner part of the electromagnetic calorimeter for two types of target material, carbon and titanium. From the data on C and Ti the nuclear dependence of pion production was extracted. Various approaches for the luminosity determination at HERA-B are investigated. The average number of interactions in the target can be determined from the energy deposition in the electromagnetic calorimeter. This method provides a high accuracy in the luminosity determination. The feasibility to study hadronic production of dileptons in the high-mass region at HERA-B is investigated with a Monte Carlo simulation. The predicted mass resolution of Upsilon mesons will allow the clear observation of the Upsilon mass peak above the background, and to separate the Upsilon(1S) and Upsilon(2S) states. The possibility to perform an accurate measurement of polarization of Upsilon mesons is demonstrated. This measurement provides an excellent opportunity to test different mechanisms of heavy quarkonium production.

Les travaux de thèse présentés dans ce mémoire s’inscrivent dans le cadre du projet ANR BARPPRO. Ce programme de recherche vise à étudier l’influence d’une barrière de protection face à une explosion en régime de détonation. L’objectif est d’établir des méthodes de calcul rapides de classement des zones d’effets pour aider les industriels au dimensionnement des barrières de protection. L’une à partir d’abaques, valable pour des configurations en géométrie 2D, sur des plages spécifiées de paramètres importants retenus, avec une précision de +/- 5%. L’autre à partir d’une méthode d’estimation rapide basée notamment sur les chemins déployés, valable en géométrie 2D et en géométrie 3D, mais dont la précision estimée est de +/- 30%. Afin d’y parvenir, l’étude s’appuie sur trois volets : expérimental, simulation numérique et analytique. La partie expérimentale étudie plusieurs géométries de barrière de protection à petites échelles pour la détonation d’une charge gazeuse (propane-oxygène à la stoechiométrie). Les configurations expérimentées servent à la validation de l’outil de simulation numérique constitué du solveur HERA et de la plateforme de calcul TERA 100. Des abaques d’aide au dimensionnement ont pu être réalisés à partir de résultats fournis par l’outil de simulation (3125 configurations de barrière de protection, TNT). L’étude des différents phénomènes physiques présents a également permis de mettre en place une méthode d’estimation rapide basée sur des relations géométriques, analytiques et empiriques. L’analyse de ces résultats a permis d’établir quelques recommandations dans le dimensionnement d’une barrière de protection. Les abaques et le programme d’estimation rapide permettent à un ingénieur de dimensionner rapidement une barrière de protection en fonction de la configuration du terrain et de la position de la zone à protéger en aval du merlon. / This thesis is a part of the ANR BARPPRO project. This research program studies this influence of the protection barrier during an explosion detonation. The goal of this project is to establish fast-computation methods of area classification effects to help the industrial to design the protection barrier on the SEVESO sites. One from abacus, for configurations in 2D geometry on specified parameters used, with an accuracy of +/- 5%. The other from a fast-running method based on broken lines for configurations in 2D and 3D geometries, but the accuracy is +/- 30%. This study includes three approaches: experimental, numerical simulation and analytical approaches. The experimental part studies several geometries of the protection barrier for a gaseous explosion (stoichiometric propane-oxygen mixture) at small scales. The experimental configurations used to validate the numerical simulation tool constituted of the HERA software and the TERA 100 supercomputer. The overpressure charts were able to generate from the numerical results (3125 configurations of the barrier for a TNT charge). The analysis of these results allows to establish different recommendations in the design of the protection barrier. The study of the different physical phenomena present has also helped to set up a fast-running method based on the geometrical, empirical and analytical relations. All these tools will enable an engineer to analyze and estimate the evolution of overpressure around the barrier as a function of the site’s dimensions.

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In dieser Arbeit wird die Erzeugung der Charmonium-Zustände J/psi und psi(2S) in Proton-Kern-Reaktionen bei Schwerpunktsenergien von 42 GeV untersucht. Die Daten wurden mit dem HERA-B-Experiment aufgenommen, das in HERA den Protonstrahl nutzt, um Protonen an den Kernen verschiedener Drahttargets zu streuen. Mehr als 150 000 J/psi und 2400 psi(2S)-Zerfälle in Myon-Paare wurden beobachtet. Die HERA-B-Daten decken den kinematischen Bereich in Feynman-x (x_F) zwischen -0.36 und 0.10 und im Transversalimpuls (p_T) bis 4.5 GeV/c ab. Die x_F - und p_T-Verteilungen für die Produktion von J/psi und psi(2S) wurden für Kohlenstoff- und Wolfram-Targets gemessen. Die x_F-Verteilung stimmt gut mit nicht-relativistischen QCD-Rechnungen überein. Bei der p_T-Verteilung findet man einen klaren Anstieg des mittleren p_T für schwerere Kerne: Kohlenstoff = 1.244 +- 0.003 +- 0.034 GeV/c und Wolfram = 1.336 +- 0.004 +- 0.041 GeV/c. Der Vergleich der Erzeugungsraten von psi(2S) und J/psi ergibt: (B''_{muon muon} sigma(psi(2S)) ) / (B_{muon muon} sigma(J/psi)) = 165 +- 9 +- 4 ( x 0.0001) für Kohlenstoff und 154 +- 16 +- 8 ( x 0.0001) für Wolfram. Diese Verältnisse wurden auch für die x_F - und p_T-Verteilungen bestimmt. / In this thesis the production of the charmonium states J/psi and psi(2S) in proton-nucleus collisions at a center-of-mass energy of 42 GeV is studied. The data have been taken by the HERA-B experiment which uses the HERA proton beam to scatter protons off the nuclei of different wire targets. Over 150 x 10^3 J/psi and 2400 psi(2S) decaying to muon pairs are observed. The HERA-B data cover the kinematical range in Feynman x (x_F) between -0.36 and 0.10 and in transverse momentum (p_T) up to 4.5 GeV/c. The x_F and p_T differential distributions for the production of J/psi and psi(2S) mesons are measured for carbon and tungsten target materials. The J/psi x_F distribution agrees well with non-relativistic QCD calculations. From the p_T distributions we find a clear increase of the average p_T for heavier nuclei: Carbon = 1.244 +- 0.003 +- 0.034 GeV/c and Tungsten = 1.336 +- 0.004 +- 0.041 GeV/c. We compared the production rates of psi(2S) to J/psi mesons: (B''_{muon muon} sigma(psi(2S)) ) / (B_{muon muon} sigma(J/psi)) = 165 +- 9 +- 4 ( x 0.0001) for carbon and 154 +- 16 +- 8 ( x 0.0001) for tungsten. These ratios have also been determined for the x_F and p_T distributions.

DNA is constantly subjected to chemical and mechanical damage. The ability to repair the lesions sustained is essential for all life. Double stranded DNA (dsDNA) breaks are especially toxic as both antiparallel strands of DNA are severed. The most high fidelity mechanism available to repair this damage is homologous recombination, a mechanism that uses homology from the sister chromatid to replace any lost information. Key proteins involved in maintaining genomic stability this way are conserved in all domains of life. One such component is the Mre11/Rad50 complex that is involved in the initial recognition of damage and recruitment of subsequent repair factors. Understanding the function of this DNA repair complex and any associated proteins has implications for human cancers and aging. The proteins of thermophilic archaea present an excellent opportunity to study these systems in a robust, tractable and eukaryote-like system. Archaea are in many ways biochemically unique, for example they are the only domain capable of methanogenesis. However archaea share a high level of homology with eukaryotes in many essential cellular processes such as DNA replication, homologous recombination and protein degradation. In thermophilic archaea the mre11/rad50 genes are clustered in an operon with the herA/nurA genes that form a helicase/nuclease complex. This has lead to speculation that the four proteins work together during homologous recombination to produce the 3' overhangs required by RadA to identify homology. As part of this investigation I have performed extensive bioinformatic searches of a variety of archaeal/bacterial systems. These analyses have revealed operonic linkages to other known recombinational helicase/nucleases, such as AddAB and RecBCD. These genomic linkages are especially prevalent in thermophilic organisms suggesting their functional relevance is particularly acute in organisms exposed to a high amount of genomic stress. Comparison of the evolutionary trees, constructed for each protein, makes a single genomic linkage event the most likely scenario, but cannot definitively exclude other possibilities. Exhaustive attempts were made to demonstrate an interaction between Mre11/Rad50 and HerA/NurA. Despite analysis by nickel/cobalt pulldown, immunoprecipitation, analytical gel filtration, ITC and OCTET an interaction could not be confirmed or definitively dismissed. However in the process an interesting Rad50 tetrameric assembly was identified and attempts were made to crystalize it. Hexameric helicases and translocases are key to the replication and DNA packaging of all cellular life and multiple viruses. The hexameric translocase HerA is a robust model for investigating the common features of multimeric ATPases as it is extremely stable and experimentally tractable. Here it is revealed that HerA exists in a dynamic equilibrium fluctuating between hexameric and heptameric forms with rapidly interchanging subunits. This equilibrium can be shifted to heptamer by buffering conditions or towards the hexamer by the physical interaction with the partnering nuclease NurA, raising the possibility that these alternate states may play a role in translocase assembly or function. A novel C-terminal brace, (revealed by a collaborative crystallographic structure) is investigated; as well as stabilizing the assembly, this brace reaches over the ATPase active site of its neighbouring subunit. It is seemingly involved in the conversion of energy generated by ATP hydrolysis into physical movement in the central channel of the hexamer. The regulation of homologous recombination is extremely important to prevent aberrant activity, resulting in mutations and genome reorganization. In eukaryotic organisms, it is well established that post-translational modifications and protein turnover at the proteosome play important roles in this control. In particular, there is significant interest currently in the ubiquination-proteasome destruction pathway as a mechanism for extracting DNA repair components from chromatin at the termination of the DNA repair process. To date no Ubiquitin proteins have been identified in the Archaea, however related proteins URMs/SAMPs (Ubiquitin Related Modifier/Small Archaeal Modifier Protein) have previously been identified. URMs are thought to have evolved from a common antecedent to eukaryotic ubiquitin and likely represent an evolutionary 'missing link' in the adaption of sulphur transfer proteins for covalent modifications. There has been speculation that Urm1 may play a similar role to ubiquitin in the proteasome degradation pathway and we have recently provided evidence to corroborate this. Here the potential for modification of Mre11/Rad50/HerA/NurA by Urm1 was investigated. Indeed Rad50 shows evidence of clear urmylation both in vivo and in vitro. Western blotting and mass spec analysis confirmed the covalent attachment of Urm1 to Rad50. Furthermore I present preliminary evidence that this urmylation can lead to the destruction of Rad50 via a direct physical interaction with the proteasome. This is the first evidence of such a regulatory system for Rad50. Investigating the urmylation and destruction of Rad50 was closely linked to investigating the archaeal proteasome, a close homologue of the eukaryotic proteasome. To date the majority of archaeal core proteasomes examined were believed to consist of only two subunits; alpha and beta. The subunits are arranged into heptameric rings, which then form an alpha/beta/beta/alpha stack with a single channel running through the centre of all four rings. Here we reveal that in Sulfolobus species the inner catalytic chambers are made up of mixed beta rings composed of two subunits. The first plays a crucial structural role but appears catalytically inert, while the second conveys catalytic activity. Here we investigate an inactive complex, containing only the structural beta subunit, and an active complex, containing both beta subunits. First, electron microscopy was performed on both complexes revealing the expected four-layered toroidal stack. Both complexes were subsequently investigated crystallographically. A 3.8 Å structure was determined for the inactive complex. As well as being one of the few archaeal core proteasome structures, this is also an important first step towards structurally investigating the novel three-subunit proteasome. The discovery of active and inactive beta subunits in the archaea brings them even closer to eukaryotic proteasomal systems, making the archaea even more valuable as model systems.

Le travail de cette thèse est consacré à la recherche de leptons excités de première génération dans les données enregistrées par l'expérience H1 auprès du collisionneur électron (positron)-proton HERA. <br /><br />Cette recherche est motivée par les approches théoriques qui étendent le modèle standard en supposant l'existence de sous-structures composites aux leptons. <br />L'ensemble des données de collisions $e^+p$ et $e^-p$ accumulées par H1 entre $1994$ et $2007$, correspondant à une luminosité intégrée de $475$~pb$^{-1}$, ont été utilisées pour cette recherche. Les analyses effectuées concernent treize topologies différentes, ce qui couvre la totalité des rapports de branchement de déexcitation de l'électron ($e^*$) et du neutrino ($\nu^*$) excités. Aucune preuve de la production de ces leptons excités de première génération n'a été observée. Des limites d'exclusions sur la section efficace de la production de leptons excités et sur le couplage $f/\Lambda$ en fonction de la masse des leptons excités sont déduites dans le cadre d'une production par interaction de gauge. Les limites obtenues dans ce cadre étendent les résultats de recherches menées précédement. <br /><br />Pour la première fois à HERA, la production possible de $e^*$ par interaction de contact a également été étudiée. Les deux modes conjoints de production par interaction de gauge et par interaction de contact, ainsi que l'interférence possible entre les deux processus, ont été considérés.

Cette thèse présente une étude exhaustive des différentes topologies d'événements à grande énergie transverse observés sur le collisionneur électron-proton HERA. L'ensemble des données accumulées par l'expérience Hl entre 1994 et 2000 ont été utilisées, ce qui représente une luminosité intégrée de 118.3 pb-1.<br> Nous avons tout d'abord participé au développement d'un nouvel environnement d'analyse orientée objet, en nous concentrant particulièrement sur la reconstruction des hadrons et des jets hadroniques. Cet environnement, qui est devenu l'outil d'analyse standard de Hl de la phase II de HERA, est mis à l'épreuve dans le cadre de notre sujet.<br> Les événements étudiés regroupent 24 topologies différentes pour lesquelles les spectres d'énergie transverse sont systématiquement étudiés. Un bon accord général au Modèle Standard est observé, mis à part dans quelques canaux à leptons isolés où plusieurs événements atypiques ont déjà été rapportés. La comparaison au Modèle Standard est quantifiée avec l'aide d'une méthode statistique spécifique développée pour l'occasion.