Cette thèse traite des systèmes de Hall quantiques en deux dimensions, dans lesquels les électrons peuvent porter plusieurs degrés de liberté discrets différents. Le ferromagnétisme de Hall quantique fournit une manière de traiter ces degrés de liberté électroniques comme des spins et isospins effectifs des électrons. Les différentes phases du système correspondent alors à différents ordres de spin ou d'isospin. En exploitant cette analogie, nous explorons différents aspects des systèmes bi-dimensionnels dans le régime de Hall quantique en étudiant la structure correspondante des spins et isospins. Ce travail consiste en trois parties qui analysent différents matériaux bi-dimensionnels dans le régime de l'effet Hall quantique. Dans chaque projet, nous utilisons la théorie de Hartree-Fock pour étudier le système à plusieurs composantes de spin et d'isospin dans l'approximation de champ moyen. Toutes nos considérations sont directement stimulées par des résultats expérimentaux. Notre motivation principale est d'obtenir une compréhension plus profonde des processus physiques et des mécanismes qui déterminent les propriétés des matériaux à partir d'investigations exclusivement théoriques de modèles abstraits. Nous espérons que cela permettra par la suite de tirer des conclusions sur les expériences, de donner des explications aux phénomènes observés ainsi que de donner des perspectives pour des investigations futures. / The present thesis deals with two-dimensional quantum Hall systems in which the electrons may be endowed with multiple discrete degrees of freedom. Quantum Hall ferromagnetism provides a framework to treat these electronic degrees of freedom as effective spins and isospins of the electrons. Different orderings of the electronic spins and isospins then characterise different possible phases of the system. Using this analogy, various aspects of the two-dimensional systems in the quantum Hall regime are explored theoretically by studying the corresponding spin and isospin structure. The work consists of three parts in which different two-dimensional materials are investigated in the quantum Hall regime. In any of the three projects presented within this thesis, Hartree Fock theory is employed to study the multicomponent spin and isospin system at the mean field level. All our considerations are stimulated directly by experimental results. We draw our main motivation from the key idea that purely theoretical investigations of abstract models may us allow to obtain deeper insights into the physical processes and mechanisms that determine the properties of the materials. This, in turn, we hope to allow conclusions about the experiments by providing possible explanations of the phenomena observed, as well as prospects for future investigations.

Unter Benutzng von 90.4/fb Daten, die das BABAR-Experiment in den Jahren 1999 bis 2002 genommen hat, wurden die Zerfälle Ds*+ -> Ds+ pi0 und Ds*+ -> Ds+ gamma mit zwei verschiedenen Methoden rekonstruiert. Die Rekonstruktions-Effizienzen wurden mittels Signal-Monte Carlo-Ereignissen und D*0-Zerfällen ermittelt. Auf diese Weise wurde das Partialbreiten-Verhältnis Gamma(Ds*+ -> Ds+ pi0) / Gamma(Ds*+ -> Ds+ gamma) auf vier verschiedene Weisen gemessen. Zusätzlich wurde das Partialbreiten-Verhältnis Gamma(D*0 -> D0 pi0) / Gamma(D*0 -> D0 gamma) gemessen. / Using 90.4/fb of data taken at the BABAR experiment in the years 1999 to 2002, the decays Ds*+ -> Ds+ pi0 and Ds*+ -> Ds+ gamma have been reconstructed with two different methods. Signal Monte Carlo events as well as D*0 decays have been used to determine the reconstruction efficiencies. Thereby, the partial widths ratio Gamma(Ds*+ -> Ds+ pi0) / Gamma(Ds*+ -> Ds+ gamma) has been measured in four different ways. Additionally, the partial widths ratio Gamma(D*0 -> D0 pi0) / Gamma(D*0 -> D0 gamma) has been measured.

Unter Benutzng von 90.4/fb Daten, die das BABAR-Experiment in den Jahren 1999 bis 2002 genommen hat, wurden die Zerfälle Ds*+ -> Ds+ pi0 und Ds*+ -> Ds+ gamma mit zwei verschiedenen Methoden rekonstruiert. Die Rekonstruktions-Effizienzen wurden mittels Signal-Monte Carlo-Ereignissen und D*0-Zerfällen ermittelt. Auf diese Weise wurde das Partialbreiten-Verhältnis Gamma(Ds*+ -> Ds+ pi0) / Gamma(Ds*+ -> Ds+ gamma) auf vier verschiedene Weisen gemessen. Zusätzlich wurde das Partialbreiten-Verhältnis Gamma(D*0 -> D0 pi0) / Gamma(D*0 -> D0 gamma) gemessen. / Using 90.4/fb of data taken at the BABAR experiment in the years 1999 to 2002, the decays Ds*+ -> Ds+ pi0 and Ds*+ -> Ds+ gamma have been reconstructed with two different methods. Signal Monte Carlo events as well as D*0 decays have been used to determine the reconstruction efficiencies. Thereby, the partial widths ratio Gamma(Ds*+ -> Ds+ pi0) / Gamma(Ds*+ -> Ds+ gamma) has been measured in four different ways. Additionally, the partial widths ratio Gamma(D*0 -> D0 pi0) / Gamma(D*0 -> D0 gamma) has been measured.

Thesis advisor: Kevin S. Bedell / We investigate the structure of the equation of state of finite nuclear matter by examining the nature of isospin dependence in the (a)symmetry energy term. In particular, we include in the description of the binding energy fourth-order dependence with respect to the asymmetry factor, (N-Z)/A, and the regime of the l=0 Landau parameter, F0´ , is required to be less than –1. This modified equation predicts a minimum binding energy where N≠Z, in addition to the standard symmetric minimum when N=Z. Results with the new asymmetry energy term are compared with experimental binding and symmetry energies from standard semi-empirical mass formulas. Importantly, this method reveals one possible mechanism for producing the phenomenon of neutron excess which is seen in physical nuclei. / Thesis (BS) — Boston College, 2004. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Physics. / Discipline: College Honors Program.

In 2008 a large statistics sample of approximately 1·107 η-decays has been collected with the WASA detector at COSY using the pd→3Heη reaction at the beam kinetic energy of 1 GeV. These data are being used to study the not so rare η decays involving charged pions, like η→π+π-π0. This decay proceeds mainly via a strong isospin violating contribution, where the decay width is proportional to the light quark mass difference squared, (md-mu)2. In addition this decay can be used to search for C-violating effects. The analysis is presented and the Dalitz plot parameters with statistical and systematical uncertainties are determined from a sample of 1.33·105 η→π+π-π0 events in the Dalitz plot. The asymmetry parameters with statistical uncertainties are presented which show no evidence of C-violation. / WASA-at-COSY

Buvo parodyta, kaip gali būti naudojama JAHN programa darbui su atominėmis ir branduolinėmis būsenos funkcijomis izosukinio bazėje. Visa informacija apie atomines ar konfigūracines būsenos funkcijas gali būti pateikta įprastame formate. Tokia tvarka leistų greitą priėjimą prie reikiamų duomenų ir paprastą komandų valdymą. Būsenos funkcijų klasifikacijas izosukinio bazėje, viendalelius kilminius koeficientus CFP, dvidalelius kilminius koeficientus CFGP, transformacijos matricas iš LS ryšio į izosukinio ryšio bazę galima surasti naudojant atitinkamas komandas, kurių sintaksė yra analogiška literatūroje naudojamiems žymėjimams. Trumpas ir efektyvus sluoksnių ir konfigūracinių būsenų įvedimas daro programą atsparesnę klaidoms ir leidžia vartotojui sukurti atskiras koeficientų lenteles tam tikriems sluoksnių būsenų termams izosukinio bazėje. Tokios lentelės gaunamos vienos komandinės eilutės pagalba. Tikimasi, kad JAHN programa padės smulkiau analizuoti įvairių fizikinių operatorių matricinius elementus izosukinio bazėje. Komandos jj ryšiui, analogiškai kaip ir LS ryšiui, yra pateikiamos kuo mažiau nutolstant nuo jų užrašymo formos knygose ar straipsniuose. Įvedant nesudėtingas komandas nustatome sluoksnio charakteristikas. CFGP reikšmės irgi randamos JAHN programa, kas gerokai sutaupo laiko, kadangi jų nereikia ieškoti spausdinamose lentelėse. / We have shown how JAHN has been used for dealing with atomic or nuclear state functions within an isospin basis. All information about the atomic or the configuration state functions can be stored in a suitable format in order to allow a fast access and manipulation. Apart from the classification of the shell states in an isospin basis the coefficients of fractional parentage, the coefficients of fractional grandparentage, the transformation matrices for going from LS – coupled to an isospin – coupled basis can be calculated interactively. A short and powerful notation has been introduced for the shell and configuration states which makes the program less prone to errors and which enables the user to create an electronic table of shell state terms or CFP in isospin basis within only a single command line. The JAHN program will support a more detailed analysis of the matrix elements of various physical operators by using an isospin basis. The algorithms for jj coupling is analogous with LS coupling and they are presented in the way, which is commonly used in printed books and articles. We define layer characteristics from ordinary commands. CFGP values are also calculated with JAHN program, which is very convenient for saving the time that is needed to look up for those values in the printed tables.

Techn. University, Diss., 2004--Dresden.

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Future long baseline neutrino oscillation experiments like the Deep Underground Neutrino Experiment (DUNE) rely on Liquid Argon Time Projection Chamber (LArTPC) detectors. The reconstruction of neutrino flavors and energy through interactions with Argon is a critical issue for assuring the DUNE success. The neutrino-Argon nuclear cross section is one of the biggest sources of uncertainty in measuring possible Charge-Parity Violation (CPV) in the neutrino (ν) sector and decoupling background like matter-effects. This thesis summarizes the exclusive electron scattering measurement of the Jefferson Lab E12-14-012 experiment. The E12-14-012 experiment goals are to explore the Ti(e,e′p) and Ar(e,e′p) reactions in a wide range of kinematics in order to determine the spectral function of protons and neutrons in Argon. The measurements made in E12-14-012 are the first of their kind in argon and are a pivotal step in understanding the electron-Argon interaction and its relation to neutrino scattering. Titanium was specifically chosen under an assumption that its protons can be a proxy for argon neutron spectral functions. The analysis of the exclusive electron scattering in titanium is described in detail in this thesis. / M.S. / While considerable progress has been made in understanding the power of the atom, nucleons (protons and neutrons) trapped in medium-to-heavy nuclei have properties that we still need to understand. The purpose of this thesis is to explore the nuclear investigation conducted at Jefferson Lab (JLab) in Newport News, Virginia. Specifically, we follow the data analysis of the JLab Hall A Experiment E12-14-012 which seeks to quantify the nuclear energy momentum distributions of nucleons in complex nuclei like titanium and argon. These measurements, the first of their kind experimentally, are done to provide a reliable model for lepton-nucleus interactions. Modeling lepton-nucleus interactions in argon is of paramount importance, as argon is the primary target medium in future long baseline neutrino oscillation experiments like DUNE. Neutrinos are notoriously difficult to measure; and therefore, when they interact, we only measure the interaction products as they come out of the nucleus. Sometimes the products of the primary interaction will not escape the nucleus and have to be modelled to accurately estimate the incoming neutrino energy. The analysis on titanium provided in this thesis is a bridge for argon interactions with leptons, where titanium is used to determine argon neutron momentum and energy distributions.