Abstract The neutral B mesons B0 and B0s can under go flavor changing oscillations due to interactions by the weak force. Experiments which measure the frequency of these state transitions produce extremely noisy results that are difficult to analyse. A method for extracting the frequency of B mesons oscillations using the continuous wavelet transform is developed here. In this paper the physics of B meson mixing is related, leading to the derivation of a function describing the expected amount of mixing present in B0 and B0s meson decays. This result is then used to develop a new method for analysing the underlying frequency of oscillation in B mixing. An introduction to wavelet theory is provided in addition to details on interpreting daughter wavelet coefficient diagrams. Finally, the effectiveness of the analysis technique produced, referred to as the Template Fitting Method, is investigated through an application to data generated using Monte Carlo methods.

Nous rapportons les résultats d'une étude des désintégrations semileptoniques non-charmées B^+--> êta^(') l^+v et B^0--> pi^- l^+v, mesurés par le détecteur BABAR avec une production d'environ 464 millions de paires de mésons BBbar issues des collisions e^+e^- à la résonance Upsilon(4S). L'analyse reconstruit les événements avec une technique relâchée des neutrinos. Nous obtenons les rapports d'embranchement partiels pour les désintégrations B^+--> êta l^+v et B^0--> pi^- l^+v en trois et douze intervalles de q^2, respectivement, à partir desquels nous extrayons les facteurs de forme f_+(q^2) et les rapports d'embranchement totaux B(B^+--> êta l^+v) = (3.39 +/- 0.46_stat +/- 0.47_syst) x 10^-5 et B(B^0--> pi^- l^+v) = (1.42 +/- 0.05_stat +/- 0.08_syst) x 10^-4. Nous mesurons aussi B(B^+--> êta' l^+v) = (2.43 +/- 0.80_stat +/- 0.34_syst) x 10^-5. Nous obtenons les valeurs de la norme de l'élément |V_ub| de la matrice CKM en utilisant trois calculs différents de la CDQ. / We report the results of a study of the exclusive charmless semileptonic decays, B^+--> êta^(') l^+v and B^0--> pi^- l^+v, undertaken with approximately 464 million BBbar pairs collected at the Upsilon(4S) resonance with the BABAR detector. The analysis uses events in which the signal B decays are reconstructed with a loose neutrino reconstruction technique. We obtain partial branching fractions for B^+--> êta l^+v and B^0--> pi^- l^+v decays in three and twelve bins of q^2, respectively, from which we extract the f_+(q^2) form-factor shapes and the total branching fractions B(B^+--> êta l^+v) = (3.39 +/- 0.46_stat +/- 0.47_syst) x 10^-5 and B(B^0--> pi^- l^+v) = (1.42 +/- 0.05_stat +/- 0.08_syst) x 10^-4. We also measure B(B^+--> êta' l^+v+) = (2.43 +/-0.80_stat +/- 0.34_syst) x 10^-5. We obtain values for the magnitude of the CKM matrix element |V_ub| using three different QCD calculations.

Techn. Universiẗat, Diss., 2005--Darmstadt.

Title: Construction of pseudoscalar meson amplitudes in chiral perturbation theory using a dispersive approach Author: Martin Zdráhal Department: Institute of Particle and Nuclear Physics, Faculty of Mathematics and Physics, Charles University in Prague Supervisor: RNDr. Jiří Novotný, CSc. Abstract: We have developed a method enabling a construction of two-loop 2 → 2 scatter- ing amplitudes of pseudoscalar mesons based on the dispersion and the unitarity relations. This method is illustrated on the construction of the amplitudes of all such processes in chiral perturbation theory in isospin limit taking into account strong interactions only. Then it was used for the construction of ππ scattering amplitudes and of K → 3π and η → 3π decay amplitudes including isospin breaking effects induced by different masses of the particles belonging to the same isomultiplet. These parametrizations are prepared for various phenomenological analyses of the ππ scattering lengths and of the isospin breaking effects, both of which could pro- vide us important information for the understanding of quantum chromody- namics at low energies. Finally, we have performed the phenomenological study of η → 3π decay and obtained a value of the quark mass ratio 1/R = (md − mu)/(ms − ˆm). Our conservative estimate is R = 39.6+2.5 −5.1....

Title: Study of strange particle production in jets with the ALICE experiment at the LHC Author: Vít Kučera Institute: Institute of Particle and Nuclear Physics Supervisors: RNDr. Jana Bielčíková, Ph.D., Nuclear Physics Institute of the CAS; Dr. Christian Kuhn, Institut Pluridisciplinaire Hubert CURIEN Abstract: Quark-gluon plasma is a state of matter existing under extreme energy densities and temperatures where quarks and gluons are deconfined. Complex phenomena occurring in the plasma emerge from the strong interaction of its constituents. This hot and dense strongly interacting matter can be created in ultra-relativistic heavy-ion collisions and its properties can be studied by measuring particles produced in the collisions. Partons produced in hard scatterings interact with the medium which modifies the production of particles in jets. Measurements of spectra of identified particles produced in jets represent an important tool for understanding the interplay of various hadronization mechanisms which contribute to the particle production in the medium created in heavy-ion collisions. In this thesis, we present the measurement of the pT spectra of Λ baryons and K0 S mesons produced in charged jets in central Pb-Pb collisions at the energy √ sNN = 2.76 TeV, measured in the ALICE experiment at the LHC. The...

Le plasma de quarks et de gluons est un état de matière obtenu lors de températures et de densités d’énergie extrêmes où les quarks et les gluons sont libres. Cette matière chaude et dense peut être créée dans les collisions d’ions lourds ultra-relativistes. Les mesures des spectres des particules identifiées produites dans des jets représentent un outil majeur permettant d'étudier les propriétés du plasma créé dans les collisions et d'ainsi comprendre les relations entre divers mécanismes contribuant à la production de particules dans ce milieu. Cette thèse présente une analyse des spectres en impulsion transverse des baryons Λ et mésons K0S produits dans des jets chargés lors de collisions Pb–Pb centrales à l'énergie sqrt(sNN) = 2.76 TeV mesurées avec ALICE au LHC. Les résultats sont utilisés pour discuter l'origine de l'augmentation du rapport entre baryons et mésons observée pour la production inclusive des particules dans les collisions d’ions lourds ultra-relativistes. / Quark–gluon plasma is a state of matter existing under extreme energy densities and temperatures where quarks and gluons are deconfined. This hot and dense strongly interacting matter can be created in ultra-relativistic heavy-ion collisions. Measurements of spectra of identified particles produced in jets represent a major tool for studying properties of the plasma created in the collisions and for understanding the interplay of various mechanisms which contribute to the particle production in this medium. In this thesis, we present the measurement of the transverse-momentum spectra of Λ baryons and K0S mesons produced in charged jets in central Pb–Pb collisions at the centre-of-mass energy sqrt(sNN) = 2.76 TeV, measured with ALICE at the LHC. The results of the analysis are used to discuss the origin of the enhancement of the baryon-to-meson ratio observed for the inclusive production of light-flavour particles in ultra-relativistic heavy-ion collisions.

Title: Study of the rare B-meson decays with the ATLAS experiment Author: Marek Biroš Institute: Institute of Particle and Nuclear Physics Supervisor: RNDr. Pavel Řezníček, Ph.D., Institute of Particle and Nuclear Physics Abstract: The rare B0 d → K∗0 (892) μμ decay is one of the B-physics channels sensitive to Beyond Standard Model effects. The potential deviation from Standard Model predictions could be observed in the angular distribution of this decay. The work compiles several sub-tasks at the initial stage of this complex analysis: decay angles fit validation and signal event preselection. The fit functions used in the analysis are verified on generated toy Monte Carlo data. Ranges of parameters, for which are these functions positive, are established and within this parametric space, the testing of possible intrinsic fit biases is evaluated. A dependence of the fit bias with respect to the collected number of events (expected in Run 2 as well as at HL-LHC) and to the different signal-to- background ratio is studied. The second part of the thesis deals with processing of raw reconstructed data from the detector into n-tuples resulting in a more compact dataset that would be used in the final analysis. Within the process, baseline cuts are applied in order to minimize size of final datasets by reducing...

Presented is a search for the rare hadronic B meson decay B0 -> eta phi. It is based on 86 x 10^6 BB pairs recorded by the BABAR experiment at the Stanford Linear Accelerator Center between 1999 and 2002. phi mesons are reconstructed in the channel phi -> K+ K-. eta mesons are reconstructed in the channels eta -> gamma gamma and eta -> pi+ pi- pi0. Signal events are identified by a candidate counting and a maximum-likelihood method. To ensure an unbiased measurement, the number of signal events is blinded throughout the analysis. Although no significant signal is found by either method, the maximum-likelihood method obtains a smaller statistical uncertainty. In this method, the branching fraction of the decay B0 -> eta phi is determined by the upper limit BR (B0 -> eta phi) < 3.28 x 10^-6 (90%). This value includes a systematic uncertainty of 6.2%. The cited upper limit is consistent with recent theoretical predictions. Therefore, this search gives no indication for particle interactions that are not described by the Standard Model of particle physics. / Vorgestellt wird eine Suche nach dem seltenen hadronischen B-Meson-Zerfall B0 -> eta phi. Sie basiert auf 86 x 10^6 BB-Paaren, die zwischen 1999 und 2002 vom BABAR-Experiment am Stanford Linear Accelerator Center aufgezeichnet wurden. phi-Mesonen werden im Kanal phi -> K+ K- rekonstruiert. eta-Mesonen werden in den Kanälen eta -> gamma gamma und eta -> pi+ pi- pi0 rekonstruiert. Zur Identifikation von Signalereignissen wird eine Abzählmethode und eine Maximum-Likelihood-Methode verwendet. Um eine unvoreingenommene Messung zu gewährleisten, bleibt die Anzahl der Signalereignisse während der gesamten Analyse blind. Durch keine der verwendeten Methoden wird ein signifikantes Signal nachgewiesen. Die Maximum-Likelihood-Methode liefert jedoch eine kleinere statistische Unsicherheit. In dieser Methode ist das Verzweigungsverhältnis des Zerfalls B0 -> eta phi durch die obere Grenze BR (B0 -> eta phi) < 3.28 x 10^-6 (90%) gegeben. Dieser Wert enthält eine systematische Unsicherheit von 6.2%. Die angegebene obere Grenze ist mit aktuellen theoretischen Vorhersagen konsistent. Damit gibt diese Untersuchung keine Hinweise auf Wechselwirkungen, die nicht durch das Standardmodell der Elementarteilchenphysik beschrieben werden.

Les études des propriétés et du mécanisme de la production du charmonium ont débuté avec la découverte du méson J/ψ. Depuis plus de 40 ans, le mécanisme de production de charmonium n'est toujours pas clair. Les états de charmonium sont copieusement produits dans les collisionneurs hadroniques, ce qui permet d'étudier systématiquement leurs paramètres de résonance, leur production et leurs désintégrations. En dépit des taux de production élevés, de nombreux états de charmonium sont peu étudiés suite aux difficultés de leur reconstruction avec le bruit de fond important. L’expérience LHCb offre une opportunité unique d’étudier les états S et P de charmonium en utilisant leurs désintégrations vers des hadrons, et en particulier la production des états ηc et χc. Selon le formalisme de la QCD non relativiste (NRQCD), les éléments de matrice décrivant l’hadronisation des états S (ou P) du charmonium sont liés. Par conséquent, les mesures LHCb fournissent les nouveaux tests rigoureux de NRQCD. Dans le cadre de la thèse, la première mesure de la section efficace de production de l’état ηc(1S) à √s=13 TeV et la mesure la plus précise de la masse sont effectués, avec la désintégration de l'état ηc(1S) vers proton et antiproton. De plus, la production des états χc et ηc(2S) dans les désintégrations des hadrons b est étudiée en utilisant leurs désintégrations vers φφ. Les résultats obtenus sont confrontés aux prédictions de modèles théoriques. L’analyse phénoménologique originale démontre que la description de la production de charmonium dans les collisions hadroniques et de la production dans les désintégrations inclusives des hadrons b dans la gamme entière des impulsions transverses demeure un défi. / Studies of charmonium properties and production mechanism started with the discovery of J/ψ meson. Since more than 40 years the charmonium production mechanism is still not entirely understood. Following the era of investigations at e⁺e⁻ machines, nowadays, charmonium states are copiously produced at hadron colliders, that allows systematic studies of their resonance parameters, production observables and decays. Despite large production rates, many charmonium states are barely studied due to the complications of their reconstruction against a large background level. The LHCb experiment provides a unique opportunity to study S-wave and P-wave charmonium states using their decays to hadrons. This allows measuring production observables of ηc and χc charmonium states. According to the theoretical formalism of Non-Relativistic QCD (NRQCD), the production observables of the same wave charmonium states are linked. Hence, the LHCb measurements provide a series of stringent tests of NRQCD. In the framework of this thesis, the first measurement of the ηc(1S) differential production cross-section at √s=13 TeV and the most precise to date single mass measurement are performed, where the ηc(1S)$ state is reconstructed via its decay to proton and antiproton. In addition, the production of the χc and ηc(2S) states in b-hadron decays is studied using decays to φφ. The obtained results are confronted with existing theory predictions. The original phenomenological analysis concludes that the description of charmonium prompt production and production in inclusive b-hadron decays in an entire range of transverse momentum remains a challenge.

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