京都大学 / 0048 / 新制・論文博士 / 博士(理学) / 乙第13368号 / 論理博第1572号 / 新制||理||1666(附属図書館) / 京都大学理学研究科 / (主査)教授 永江 知文, 教授 中家 剛, 准教授 成木 恵 / 学位規則第4条第2項該当 / Doctor of Science / Kyoto University / DGAM

In einer systematischen Analyse wird die Produktion von ω-Mesonen in Proton-Proton-Kollisionen pp → ppω untersucht. Die Messung der experimentellen Daten wurde mit dem Flugzeitspektrometer COSY-TOF am Forschungszentrum Jülich für vier verschiedene Überschussenergien (ε = 92, 128, 129 und 173 MeV, ε = √s − 2 · mp − mω) durchgeführt. In der Analyse werden Ereignisse, in denen das kurzlebige ω-Meson über den Hauptzerfallskanal ω → π+π−π0 in drei Pionen zerfällt, gegenüber denen anderer Reaktionskanäle angereichert. Die Reaktion pp → ppω wird anschließend anhand der Signale in den Spektren der Missing Mass, das ist die im Ausgangskanal neben der invarianten Masse des Proton-Proton-Systems fehlenden Masse, untersucht. Totale sowie differentielle Wirkungsquerschnitte werden in verschiedenen Bezugssystemen bestimmt, u. a. die Winkelverteilungen der Protonen und ω-Mesonen im Schwerpunktsystem, Verteilungen von Jackson- und Helizitätswinkeln sowie die Spektren der invarianten Massen. Darüber hinaus wird mit Hilfe der Bestimmung der Zerfallsebenen der ω-Mesonen die Polarisation der ω-Mesonen ermittelt. Im Dreiteilchenausgangszustand ppω werden Bahndrehimpulse l > 0 nur für die ω-Mesonen gefunden. Aus der Messung folgt, dass bei ε = 92, 128 und 129 MeV maßgeblich Endzustände mit Bahndrehimpulsen lω = 0 ħ und lω = 1 ħ sowie bei ε = 173 MeV zusätzlich solche mit lω = 2 ħ zum Reaktionsprozess beitragen. Weitere Informationen über die beteiligten Partialwellen werden aus der Messung der Polarisation der ω-Mesonen gewonnen. Direkte Hinweise auf Beiträge von Nukleonresonanzen zum Produktionsprozess werden in keiner der untersuchten Observablen gefunden. Ein Szenario, in dem ω-Mesonen ausschließlich über Nukleonresonanzen produziert werden, kann anhand der Winkelverteilungen von Protonen und ω-Mesonen ausgeschlossen werden. / A systematic analysis of the production of ω mesons in proton-proton collisions pp → ppω is carried out. The experimental data were taken at Forschungszentrum Jülich with the COSY-TOF spectrometer at four different excess energies (ε = 92, 128, 129 and 173 MeV, ε = √s − 2 · mp − mω). In the analysis events with ω-mesons decaying via the main decay channel ω → π+π−π0 are enriched in relation to other reaction channels. Afterwards, the reaction pp → ppω is analysed based on the ω-signals in the spectra of the missing mass, i. e. the mass missing in the exit channel beside the proton-proton system. Total as well as differential cross sections are determined in different reference systems (angular distributions of ω-mesons and protons in CMS, distributions of Jackson and helicity angles, and invariant mass spectra). In addition the polarisation of the ω-mesons is determined. In the three particle exit channel ppω angular momenta l > 0 are seen only for ω-mesons. It is found that final states with angular momenta lω = 0 ħ and lω = 1 ħ contribute at excess energies ε = 92, 128 and 129 MeV. In addition states with lω = 2 ħ are seen at ε = 173MeV. Further informations on partial waves follows for the polarisation of the ω-meson. No observable shows direct signs of resonant contributions to the production process. In contrast, using the informations from the angular distributions of ω-mesons and protons a scenario with the exclusive production of ω-mesons through N* resonances can be excluded.

No description available.

NIL

The TOF-spectrometer located at the proton accelerator COSY (Juelich) stands out for experimental versatility. This is due to its modular setup: about ten subdetectors can be be arranged to satisfy the individual requirements of specific experiments. However, this flexibility hampers the calibration and the data analysis, since for each new detector setup the software has to be adjusted as well. Therefore, a new analysis framework (TofRoot) has been developed. A set of concepts is used that enables teamwork and leads to an efficient data-analysis, even for different beamtimes. Using TofRoot, three reactions are analyzed - each for two different beam momenta (2950 MeV/c, 3200 MeV/c): Firstly, the elastic proton-proton scattering. It is used to determine the luminosity and to extract benchmark results for the detector performance. Secondly, the reaction pp->deutoron-piplus is studied. Total as well as differential cross sections are presented, which nicely fit into the word data set. Finally, the vector-meson production (omega) is investigated which is the scientific focus of this work. Here, the theoretical and experimental knowledge is presently rather scarce. However, the elementary reaction dynamics is needed as an inevitable prerequisite in many fields of physics; e.g. the short range part of the nucleon-nucleon force, the description of extremely dense matter, the strangeness content of nucleons. After a detailed description of the analysis strategies, total cross sections, angular distributions, and invariant-mass spectra are presented. Some of the findings are completely new, and all provide smaller experimental uncertainties with respect to the available word data set. Finally, the results are embedded into the existing body of data and their implication on the theoretical models is discussed. / Das TOF-Spektrometer am Protonen-Beschleunigerring COSY (Juelich) besticht durch seine experimentelle Vielseitigkeit, da der modulare Aufbau aus ca.~zehn Subdetektoren eine individuelle Anpassung an spezifische experimentelle Erfordernisse ermoeglicht. Diese Flexibilitaet erschwert jedoch die Kalibrierung und die Datenauswertung, da die Software nach jedem Umbau angepasst werden muss. Daher wurde das Analyseframework TofRoot entwickelt, welches durch einen Satz von Strategien eine effiziente und teamorientierte Auswertung ermoeglicht, sogar fuer verschiedene Strahlzeiten. Mit Hilfe von TofRoot wurden drei Reaktionskanaele analysiert, jeweils fuer zwei Strahlimpulse (2950 MeV/c, 3200 MeV/c): Zuerst die elastische Proton-Proton Streuung, welche der Luminositaetsbestimmung dient und an Hand derer die Guete des Detektorsystems und der Kalibration veranschaulicht wird. Anschliessend folgt die Reaktion pp->deuteron-piplus, bei der die extrahierten Winkelverteilungen und totalen Wirkungsquerschnitte sich widerspruchsfrei in die vorhandene Datenbasis einordnen. Schliesslich wird die Vektormesonenproduktion (omega) untersucht, die den wissenschaftlichen Fokus dieser Arbeit darstellt. In diesem Kanal ist die experimentelle Datenbasis duenn und die theoretische Beschreibung bislang unvollstaendig. Ein gutes Verstaendnis der omega-Produktionsdynamik ist aber unabdingbar fuer die theoretische Beschreibung vieler Felder moderner Physik, z.B. des kurzreichweitigen Teils der Nukleon-Nukleon-Wechselwirkung, extrem dichter Materie und des Strangenessanteils im Nukleon. Nach einer detailierten Beschreibung der Analysestrategien werden totale Wirkungsquerschnitte, Winkelverteilungen und Spektren invarianter Massen vorgestellt. Verglichen mit vorhandenen Daten sind alle Angaben mit kleineren experimentellen Unsicherheiten behaftet, und zum Teil erschliessen sie zuvor nicht zugaengliche Groessen. Abschliessend werden die Ergebnisse in die vorhandene experimentelle Datenbasis eingeordnet, und ihre Auswirkung auf theoretische Modelle wird diskutiert.

In this thesis, novel corrections to B → X˦ and B → Xl+l- decays, where X is a pseudoscalar or vector meson, are presented. These are the chromomagnetic matrix element, weak annihilation in a general four-quark operator basis and a long-distance charm loop contribution. The calculation of the chromomagnetic matrix element completes the calculation of matrix elements for all relevant effective weak operators in B → V decays, removing an infrared divergence which previous computations had treated in a very approximate way. It also encounters an interesting technical obstacle not previously seen in sum rule calculations, which is likely to be encountered regularly in future once higher order loop diagrams are calculated. The potential for this term to contribute to the CP asymmetry in D → V˦ in the presence of new physics is discussed. The improved computation of weak annihilation diagrams is applied to the analysis of isospin asymmetries in radiative and semi-leptonic B → (p;K(*)) decays, and the computation of long distance charm bubble terms is applied to produce an improved prediction for time-dependent CP asymmetries in various B → V decays.

No description available.

This thesis presents measurements of the branching fractions B(Ds -> lvl) and mea- surements of the pseudoscalar decay constant, fDs , using all the data acquired at the BaBar detector at SLAC National Accelerator Laboratory, which were collected from September 1999 to April 2007, and comprised 531 fb-1. The following mea- surements are made: B(Ds -> eve) = (6:11 +/-0:38 +/- 0:33) * 10-3, B(Ds -> tvt) = (5:06 +/- 0:34 +/- 0:50) * 10-2 , and a limit B(Ds -> eve) < 1:46 * 10-4 is obtained. Using these measurements a value of fDs = 252 +/- 6 +/- 7 +/- 1MeV is obtained, where the first uncertainties account for the statistical limitations of the data, the second uncertainties account for the systematic uncertainties, and the third uncertainties account for uncertainties associated with other physical constants (dominated by the lifetime of the Ds meson).

This thesis presents a measurement of the effective B0s decay width, ΓFS, from a single exponential fit to the flavour-specific decay channel B0s → D-s π +. This measurement is based on an integrated luminosity of 340 pb-1 recorded by LHCb in 2011 at a center of mass energy of 7TeV. The dataset is divided into two exclusive selections. B0s → D-s (( ϕ →K-K+) π-)π + only has a significant background contribution arising from combinatorial background, and the modelling of this is determined entirely by the data. B0s → D-s ((K-K* (892)0 → K+ π-))π + has a larger contribution from combinatoric and mis-identified background and provides an alternative measurement. A simultaneous fit for the effective B0s decay width is performed to both the datasets leading to the result: ΓFS = 0:668 ± 0:017 ± 0:031 ps-1 The result is then combined with information from the LHCb B0s → J/ψØ analysis leading to an improved measurement of the average B0 s decay width: Γs = 0:666 ± 0:010 ± 0:031 ps-1

This thesis reports the: cross section, parameterized differential cross section, and analyzing power (a.k.a. the photon asymmetry), for neutron production via the photodisintegration of the unpolarized deuteron at 18 MeV using linearly polarized photons. The data were collected in October 2010 using the High Intensity Gamma Source at the Duke Free-Electron Laser Laboratory located at Duke University in Durham, North Carolina. The ejectile neutrons from the photodisintegration reaction were measured using the Blowfish detector array: a spherical array of 88 BC-505 liquid organic scintillator cells which cover approximately pi steradians. The initial goal of our experiment was to perform tests on the detector characteristics and check a few potential sources of systematic error, and so uncontaminated experimental runs were only taken with the remaining beam-time. Our data are therefore not optimized for precision, and so presented a number of data analysis challenges. This thesis delineates the challenges and respective solutions. Contrary to earlier results near deuteron binding energy threshold, we see reasonable agreement with a theoretical calculation based on retarded one meson exchange with empirical cutoffs in the propagators, including: off-shell corrections, relativistic corrections and the Delta isobar degree-of-freedom. Our results show similar agreement to theory as previous experiments at 14 and 16 MeV, although we see no target length dependence: such has been observed at 20 MeV.