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A central goal of flavour physics is a precise determination of the elements of the CKM matrix, which quantifies the strength of charged-current weak interactions between quarks. Of particular interest is the angle γ in the 'b-d' unitarity triangle parameterisation of the CKM matrix. One of the most promising methods to determine γ directly is to measure CP violation in interfering B±->DK± decays, where D indicates a coherent superposition of D0 and D0bar, both of which decay to the same final state. When using this method it is essential to determine the hadronic decay parameters of the D precisely in order to reduce the systematic uncertainties on the measurement of γ. One such parameter is the strong-phase difference between D0 and D0bar decays, which must be accurately known across the entire kinematic phase space. In this thesis we present measurements related to the determination of γ at both the CLEO-c experiment at Cornell University and the LHCb experiment at CERN. Firstly, we describe a model-independent determination of the D->KsKK strong-phase difference using 818pb-1 of quantum-correlated D0-D0bar data collected by CLEO-c at the ψ(3770) resonance. We reconstruct D->KsKK decays tagged with a variety of final states. By studying these decays we determine the weighted cosine and sine of the strong-phase difference in bins across the Dalitz plane. We run simulations to estimate the impact of these measurements on a determination of γ using B±->D(KsKK)K± decays. The resulting uncertainty on γ due to the CLEO-c inputs is between 3.2° and 3.9°, depending on how the Dalitz plane is binned. Furthermore, we present a model-independent measurement of the CP content of the decay D0->KsKK in the kinematic region of the φ->KK resonance. The fraction of CP-odd events in this region is 0.76 or higher at the 90% C.L. We also present an analysis of data recorded by LHCb in 2010, corresponding to an integrated luminosity of 36.5pb-1. We reconstruct the decays B±->D(Kπ)h± and B±->D(KK)h±, where h± indicates either K± or π±. Although there are not enough events in this dataset to measure γ, we are able to measure other observables related to CP violation in the B±->Dh± system. We measure B(DK,Fav)/B(Dπ,Fav), the ratio of the branching fraction of B±->D(Kπ)K± to that of B±->D(Kπ)π±, to be 0.066 ± 0.005 ± 0.004, and B(DK,CP)/B(Dπ,CP), the ratio of the branching fraction of B±->D(KK)K± to that of B±->D(KK)π±, to be 0.093 ± 0.019 ± 0.005. We determine several CP asymmetries: A(CP+,DK), the CP asymmetry in B±->D(KK)K± decays, is measured as 0.06 ± 0.17 ± 0.07; A(CP+,Dπ), the CP asymmetry in B±->D(KK)π± decays, is found to be 0.009 ± 0.042 ± 0.011; and A(Fav,DK), the CP asymmetry in B±->D(Kπ)K± decays, is measured as -0.109 ± 0.085 ± 0.019. Finally we calculate R(CP+), the ratio of the branching fraction of B±->D(KK)K± to that of B±->D(Kπ)K±, to be 1.41 ± 0.31 ± 0.11. These results indicate that LHCb is in a strong position to make a world-leading measurement of γ with a larger data sample.

Two analyses are performed using data collected by the LHCb experiment during 2011. Both consider decays of charged B mesons reconstructed in the π±μ+μ− final state. Decays involving dimuons provide an experimentally clean signature, even in the high-background environment of the √s = 7 TeV proton-proton collisions at the LHC. The first analysis measures the CP asymmetry of B±→Ψπ± decays using 0.37 fb-1 of data, where the dimuon decays of two resonances are considered, J/ψ→μ+μ− and ψ(2S)→μ+μ−. The branching fraction is measured relative to the Cabibbo favoured B±→ΨK± mode. The second analysis uses 1 fb-1 of data to make the first observation of the non-resonant B±→π±μ+μ− decay. The branching fraction is measured relative to that of B±→K±μ+μ−, and measurements of the CP asymmetry and the ratio of CKM matrix elements Vtd/Vts are obtained. The branching fractions of the decays of interest are found to be B(B±→J/ψ π±) = (3.88 ± 0.11 ± 0.15) x 10-5, B(B±→ψ(2S) π±) = (2.52 ± 0.26 ± 0.15) x 10-5 and B(B±→π±μ+μ−) = (2.48 + 0.57 −0.52 ± 0.17) x 10-8, where the first uncertainty is related to the statistical size of the sample and the second quantifies systematic effects. The measured CP asymmetries in these modes are A CP (J/ψ π) = 0.005 ± 0.027 ± 0.011, A CP (ψ(2S) π) = 0.048 ± 0.090 ± 0.011 and A CP (μμπ) = -0.045 ± 0.220 ± 0.066, with no evidence of direct CP violation seen. The ratio of matrix elements is measured as Vtd/Vts = 0.274 + 0.031 − 0.028 ± 0.008, which is in agreement with previous results.

The Large Hadron Collider started operation this year, 2008. LHCb is a precision heavy-flavour experiment at this collider. The precision of LHCb is greatly aided by the LHCb Ring Imaging Cherenkov system for the separation and identification of charged hadrons. This system uses pixel Hybrid Photon Detectors, an innovative new technology for single photon imaging. The simulation and testing of these photon detectors are reported and discussed. The photodetectors were measured to have reached or exceeded the specifications in key areas. In particular, the detector quantum efficiencies far exceed expectations, by a relative 27 %. The precision of LHCb will be used to examine CP-violation and rare decays of B-mesons. A key part of the physics programme will be a measurement of the CP-violating flavour specific asymmetry in neutral B-meson mixing. This asymmetry is expected to be very small in the Standard Model, of order 10-4, however it is very sensitive to new physics, which can increase the asymmetry dramatically. We present an improved event selection and a novel method to control systematics. This will enable us to make a world-leading measurement of this parameter in one nominal year of data taking (2 fb-1).

The angle γ, with an uncertainty of approximately 10° is the least well constrained angle of the unitary triangle. Better experimental constraints on this parameter are required in order to provide a consistency check on the standard model description of CP violation. A promising strategy for measuring γ involves exploiting interference effects present in B^± → DK^± decays where the D subsequently decays to a three or four body final state. The three body decay D → K_S ⁰p⁺p^- and the four body decay D⁰ → K⁺K^-p⁺p^- are suitable candidates for making such a measurement. However independent knowledge of the decay structure of these decays is required. The impact of the model, used to describe the p⁺p^- S wave, in the D⁰ → K⁺K^-p⁺p^- decay, on the uncertainty in the measurement of γ is estimated via a simulation study. It is determined that the uncertainty on a gamma measurement would be compromised by this model uncertainty within one year of LHCb data running. The four body decay D⁰ → K⁺K^-p⁺p^- also provides a candidate for making a γ measurement. This decay is expected to display a rich resonant structure. An understanding of this decay may also provide an insight into low energy QCD in addition to allowing a search for CP violation. Only one previous amplitude analysis has been performed on this decay. Using data collected at the CLEO-II.V, CLEO-III and CLEO-c experiments an amplitude model is developed for the D⁰ → K⁺K^-p⁺p^- decay. This model is qualitatively similar to that produced in the previous analysis although the model presented in this thesis considers higher orbital angular momentum states and distinguishes between conjugate states that the previous model did not. A search for CP violation is also carried out using the D⁰ → K⁺K^-p⁺p^- decay data. A positive confirmation of CP violation at the level of sensitivity provided by this decay data would provide evidence for a level of CP violation which could not be accounted for within the standard model. No significant evidence for CP violation is observed in this decay. A toy MC study was carried out in order to determine the sensitivity to γ which may be achieved using this decay. In this study, sets of 1000 B⁺ and B^- events are generated and the decay model developed for the D → K⁺K^-p⁺p^- decay is used to describe the D decay. The sensitivity to γ determined in this study is 11°.

This thesis reports an analysis of 3.0fb^-1 of pp collision data collected by the LHCb experiment in 2011 and 2012. Decays of neutral B mesons to neutral D mesons and excited neutral kaons are reconstructed, because of their sensitivity to the CP-violating phase of the CKM matrix, γ.

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Supersymmetry is currently the best motivated extension of the Standard Model and will be subject to extensive studies in the upcoming generation of colliders. The e-e- mode would be a straight forward extension to the currently planed International Linear Collider, planned to operate in e+e- mode. The low background in this mode may prove advantageous in the study of CP- and Lepton Flavour Violtation. In this work a CP sensitive observable based on transverse beam polarisation is introduced and the impact of neutralino mixing on the total cross section in cas of non-vanishing CP-violtating phases is studied in representative scenarios including non-GUT scenarios. Additionally, the mixing of sleptons is studied in the context of LFV, an analytical approximation is developed, and possible background free measurements of these effects are investigated. / Supersymmetrie ist derzeit die bestmotivierte Erweiterung des Standardmodells und wird in der nächsten Generation von Beschleunigern intensiv studiert werden. Der e-e- Modus des geplanten International Linear Collider, welcher zunächst im e+e- Modus betrieben werden soll, stellt hier eine direkte Erweiterung da, die durch ihren niedrigen Untergrund vorteilhaft für das Studium CP- und Lepton Flavour verletzender Effekte sein kann. In dieser Arbeit wird eine CP sensitive Observable basierend auf transversaler Strahlpolarisation vorgestellt sowie der Einfluss der Neutralinomischung auf den totalen wirkungsquerschnitt im Falle nichtverschwindender CP-verletztender Phasen in repräsentativen Szenarien, auch non-GUT-Szenarien, untersucht. Ferner wird die Mischung der Sleptonen im Kontext von Lepton-Flavour-Verletzung näher beleuchtet, eine analytische Näherung entwickelt und die möglicherweise Untergrundfreie Messung dieser Effekte untersucht.

A basic assumption in fundamental physics is that equal amounts of matter and antimatter were created after the Big Bang. When particles and antiparticles collide, they annihilate, i.e. disappear and produce photons. Nevertheless, the universe consists mainly of matter today. To explain why all matter did not disappear, violation of CP symmetry beyond the Standard Model is required. CP symmetry means that the laws of physics are the same if particles are interchanged with antiparticles and spatial coordinates of all particles are mirrored. CP symmetry is relatively poorly tested in baryon decays. A new method to study CP symmetry in hyperon-antihyperon pairs has been developed at Uppsala University. Hyperons are baryons with one or more strange quarks. The method allows determining the decay asymmetry parameters of the hyperon and antihyperon separately if the hyperon-antihyperon pair is polarized. If any significant difference between the magnitudes of these parameters is found, the process is CP violating. The particle physics experiment BESIII in China is a suitable experiment to conduct this kind of measurements because it is a high precision experiment and has collected large data samples of hyperon-antihyperon pairs. The goal of this project was to study statistical precisions of the physics parameters that can be obtained with the new method in cases of J/ψ meson decaying into ΛΛ, Σ+Σ− and Σ0Σ0. High statistical precision is required to detect CP violation, because CP violating processes are, if they exist, expected to be rare. The main focus was to study the process e+e− → J/ψ → Σ0Σ0 → ΛγΛγ → pπ−γpπ+γ. In this process, CP symmetry can be tested in two decay processes: electromagnetic decay Σ0 → Λγ and weak decay Λ → pπ−. Only the asymmetry parameter of Λ → pπ− was studied. The study served as a validity check of the new method and ongoing analyses at BESIII. The statistical precision was studied by simulations: Monte Carlo data samples were created and then a maximum-log-likelihood fit was applied to the samples. An important component when determining the asymmetry parameters turned out to be the relative phase ∆φJ/ψ. The relative phase is one of the parameters used for determining the relation between the electric and magnetic form factors. ∆φJ/ψ is also related to the polarization of the hyperon-antihyperon pair. The study showed that the value of ∆φJ/ψ has a large impact on the uncertainties of the hyperon and antihyperon asymmetry parameters. A low value of ∆φJ/ψ resulted in high uncertainties and strong correlations between the asymmetry parameters. The formalism is different for different processes, which affects the uncertainties as well. The formalism used for the Σ0Σ0 process gives poorer parameter precision of the asymmetry parameter related to the Λ → pπ− decay than the formalism used for the ΛΛ process. Therefore, the ΛΛ process is a much more suitable process for CP studies of the Λ → pπ− decay. / Ett grundantagande inom den fundamentala fysiken är att lika stora mängder av materia och antimateria skapades efter Big Bang. När partiklar och antipartiklar kolliderar, annihilerar de, dvs försvinner och producerar fotoner. Trots detta består dagens universum huvudsakligen av materia. För att förklara varför all materia inte försvann krävs ett brott mot CP-symmetrin bakom standardmodellen. CP-symmetrin innebär att fysikens lagar är desamma om man byter partiklar mot antipartiklar och speglar partikelns rumsliga koordinater. CP-symmetri i baryonsönderfall är relativt dåligt testad. En ny metod för att studera CP-symmetrin har utvecklats vid Uppsala universitet för hyperon-antihyperon par. Hyperoner är baryoner med en eller fler särkvarkar. Metoden gör det möjligt att bestämma asymmetriparametrar hos hyperon- och antihyperonsönderfall separat om hyperonantihyperonparet är polariserat. Om en signifikant skillnad mellan värden av dessa parametrar upptäcks, är processen CP-brytande. Partikelfysikexperimentet BESIII i Kina är ett lämpligt experiment för sådana här mätningar eftersom det är ett högpresicionsexperiment och har dessutom samlat in stora mängder data av hyperon-antihyperonpar. Målet för detta projekt har varit att studera de statistiska precisioner av fysikparametrar som kan nås när man använder den nya metoden i de fall där J/ψ mesonen sönderfaller till ΛΛ, Σ+Σ− och Σ0Σ0. Hög statistisk precision behövs för att upptäcka CP-brott, eftersom CP-brytande processer, om de existerar, är relativt sällsynta. Huvudfokuset var att studera processen e+e− → J/ψ → Σ0Σ0 → ΛγΛγ → pπ−γpπ+γ. I denna process kan CP-symmetri testas för två sönderfallsprocesser: det elektromagnetiska sönderfallet Σ0 → Λγ och det svaga sönderfallet Λ → pπ−. I denna rapport studerades bara asymmetriparametrarna av Λ → pπ−. Detta arbete har fungerat som validitetskontroll av den nya metoden och pågående analyser på BESIII. Den statistiska precisionen undersöktes med simuleringar: Monte Carlo datamängder skapades och sedan en maximum-log-likelihood-anpassning av datan genomfördes. En viktig komponent i bestämningen av asymmetriparametrarna visade sig vara den relativa fasen, ∆φJ/ψ. Den relativa fasen är en av de parametrar som används för att bestämma relationen mellan de elektriska och magnetiska formfaktorer. ∆φJ/ψ är också relaterad till hyperonens hyperon-antihyperonparets polarisation. I forskningsprojektet visades att ∆φJ/ψ har en stor inverkan på osäkerheterna av hyperon- och antihyperonasymmetriparametrarna. Ett lågt värde av ∆φJ/ψ resulterade i stora osäkerheter och starka korrelationer mellan asymmetriparametrarna. Formalismen är annorlunda för olika processer, vilket också påverkar osäkerheterna. Formalismen som används för Σ0Σ0-processen ger sämre parameterprecision av asymmetriparametern kopplad till sönderfallet Λ → pπ− än formalismen som används för ΛΛ-processen. Därför är ΛΛ-processen en mycket lämpligare process för att testa CP-symmetrin i Λ → pπ− sönderfallet.

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