This thesis presents a measurement of the charm mixing parameters x_D and y_D in prompt D⁰&rarr; K ⁰<sub style='position: relative; left: -.6em;'>S</sub> &pi;^&plus; &pi;^&minus; decays using 1 fb^-1 of data collected by the LHCb experiment during 2011. Mixing in charm is predicted to be small within the Standard Model, but there are significant uncertainties associated with calculating the long range contributions to the decay. Recent measurements made by LHCb and others have confirmed that mixing in charm exists at a rate of less than 1 &percnt;. With LHCb due to collect more data and Belle II being commissioned, the reduction of systematic uncertainties will become increasingly important. The D⁰&rarr; K ⁰<sub style='position: relative; left: -.6em;'>S</sub> &pi;^&plus; &pi;^&minus; decay provides sensitivity to both the magnitude and relative sign between the mixing parameters. It is also one of the few channels that can measure x_D directly. It is therefore crucial to study this mode in detail as more data becomes available. The work presented in this thesis utilises a model-independent description of the K ⁰<sub style='position: relative; left: -.6em;'>S</sub> &pi;^&plus; &pi;^&minus; Dalitz plot decay for the first time in the context of charm mixing. Previous mixing measurements with this final state have used a Dalitz plot amplitude model, and the associated systematic uncertainty is not straight forward to estimate or control. In its place, this analysis uses external, statistically-limited measurements of the strong-phase difference between D⁰ and &macr;<em style='position: relative; left: -.6em;'>_D⁰ obtained by CLEO as input. In addition, a data-driven technique is used to correct for decay time biases induced by the selection removing any systematic effects due to extracting this from simulated data. As the amount of available data increases, both of these techniques will become vital to improving our understanding of mixing in charm. In the CP convention used by Babar and adopted for this thesis, the measured mixing parameters are x_D = -(0.863 &plusmn; 0.527 (stat.) &plusmn; 0.171 (syst.)) &percnt;, y_D = -(0.026 &plusmn; 0.463 (stat.) &plusmn; 0.134 (syst.)) &percnt;. Both x_D and y_D are consistent with the current world averages.

Using data equivalent to an integrated luminosity of 3 fb⁻¹ collected by the LHCb experiment during Run I (2011-2012), studies of beauty mesons decaying to a final state containing open charm are performed, concluding with a number of new results. Direct CP-violation is explored in <i>B</i>^± → <i>Dh</i>^± decays through several measurements of CP violating observables, where the charmed meson <i>D</i> is reconstructed in both 2-track and 4-track final states. A measurement of the <i>B</i>^± production asymmetry at LHCb is reported using <i>B</i>^± → <i>D</i>π^± decays, and a complementary measurement of the CP asymmetry in <i>B</i>^± → <i>J</i>/ψ<i>K</i>^± decays made. A search for the rare <i>B</i>_c− → <i>D</i>(*)π⁻ and B_c− → <i>D</i> (*)<i>K</i>⁻ decays concludes this work.

This thesis documents searches for direct CP violation in the Cabibbo-suppressed D+ to K-K+pi+ decay at the LHCb experiment. Two complementary analyses are described. Direct CP-violating asymmetries are predicted to exist in singly Cabibbo-suppressed charm decays with magnitudes of up to O(0.001) in the Standard Model, and can be enhanced to the percent level by contributions from new physics. No such asymmetry has yet been observed. The LHCb detector is a forward spectrometer with a precise vertex detector and powerful particle identification capabilities, designed to collect large, pure samples of charm and $B$ decays. Data collected at LHCb in 2010 corresponding to an integrated luminosity of 35pb^-1 are used to perform a model-independent search for direct CP violation in the D+ to K-K+pi+ decay. The Dalitz plot is divided into bins and a chi^2 test of the compatibility of the dataset with no CP violation is performed. No evidence of CP violation is found. A second search for CP violation in the region of the D+ to K-K+pi+ Dalitz plot around the phi resonance is described. The charge asymmetry in this decay is calculated and compared to that in the control channel D+ to Ks(pi+pi-)pi+. The 1.0fb^-1 of data collected at LHCb in 2011 are used. The CP-violating asymmetry is found to be (-0.04+/-0.14+/-0.14)% where the uncertainties are statistical and systematic, respectively. A new observable sensitive to CP violation that varies across the phi resonance is defined and measured, and is consistent with no CP violation at the current level of sensitivity. In addition, the CP-violating asymmetry in the decay Ds+ to Ks pi+ is determined to be (0.61+/-0.83+/-0.14)%. There is no evidence for CP violation in either channel. The prospects for new results using data collected in 2012 are very promising and a significant improvement in our understanding of these decays is anticipated.

Einer der interssantesten Prozesse im Flavour Sektor des Standard Modells (SM) im Kontext der indirekten Suche nach neuer Physik ist der seltene inklusive Zerfall B -> Xs gamma. Dieser Zerfallskanal entspricht einem neutralen Strom mit Wechsel des Flavours zwischen Anfangs- und Endzustand. Im SM ist ein solcher Uebergang unterdrueckt, da er nur ueber Schleifenbeitraege erfolgen kann, und ist somit sensitiv auf Beitraege neuer Physik. Darueber hinaus sind nichtperturbative Beitraege moderat, was praezise theoretische Vorhersagen im Rahmen einer effektiven Niederenergie Theorie ermoeglicht. Sowohl praezise Messungen als auch genaue theoretische Vorhersagen mit einer guten Kontrolle ueber perturbative und nichtperturbative Effekte sind notwendig, um den Parameterraum von Modellen jenseits des SM einzuschraenken. Experimentell wurde die Zerfallsrate B -> Xs gamma vor Allem mit Hilfe der spezialisierten Experimente BaBar und Belle an den sogenannten B Fabriken mit einer hervorragenden Genauigkeit gemessen. Um diese Praezision auch in der theoretische Vorhersage zu erhalten, sind hoehere Ordnungen in der effektiven Stoerungstheorie essentiell. Tatsaechlich fuehrt erst die Beruecksichtigung von QCD Korrekturen auf der naechst-zu-naechst-zu hoeheren Ordnung (NNLO) in Stoerungstheorie zu einer mit dem Experiment vergleichbaren theoretischen Unsicherheit. Die Bestimmung des Verzweigungsverhaeltnisses von B -> Xs gamma auf NNLO wurde innerhalb der letzten zehn Jahre von mehreren Arbeitsgruppen angegangen. Ein Gro"steil dieses Projekts wurde abgeschlossen und eine erste Abschaetzung auf diesem Niveau der Stoerungstheorie 2006 publiziert. Allerdings standen fuer diese Vorhersage nicht alle Beitraege von nach wie vor unbekannten Matrixelementen zur Verfuegung, die nur aus partiell bekannten Resultaten abgeschaetzt werden mussten. In dieser Arbeit bereiten wir einen Rahmen fuer die systematische Bestimmung der noch nicht verfuegbaren Matrixelemente auf NNLO. Ein Hauptergebnis dieser Dissertation ist die Bestimmung von fermionischen Korrekturen zu Matrixelementen von Vier-Quark Operatoren in der effektiven Theorie. Erstmalig wird hierbei die volle Massenabhaengigkeit beruecksichtigt. Ein weiterer Schwerpunkt liegt auf der Berechnung von fermionischen als auch bosonischen Korrekturen im Grenzwert einer verschwindenden Masse des Charm Quarks. Zusammen mit noch unbekannten reellen Korrekturen werden diese Ergebnisse dazu beitragen, die Unsicherheit der NNLO Vorhersage signifikant zu reduzieren. Ein wesentlicher Bestandteil dieser Arbeit, der die hier durchgefuehrten Berechnungen erst ermoeglichte, ist die Entwicklung einer automatisierten Methode zur hochpreazisen Bestimmung von Vielschleifenintegralen die zwei Massenskalen enthalten. / In the context of the indirect search for non-standard physics in the flavour sector of the Standard Model (SM), one of the most interesting processes is the rare inclusive B -> X_s gamma decay. On the one hand, being a flavour-changing neutral current, this B decay is sensitive to new physics, as it is loop-suppressed in the SM. On the other hand, it is only mildly affected by non-perturbative effects, and thus allows for precise theoretical predictions in the framework of renormalization-group improved perturbation theory. Accurate measurements as well as precise theoretical predictions with a good control over both perturbative and non-perturbative contributions have to be provided in order to derive stringent constraints on the parameter space of physics beyond the SM. On the experimental side, an outstanding accuracy in the measurement of the B -> Xs gamma decay rate has been achieved, which is mainly due the specialized experiments BaBar and Belle at the so-called B factories. To match the small experimental uncertainty, higher order computations within an effective low-energy theory of the SM are mandatory. In fact, next-to-next-to-leading order (NNLO) QCD corrections are required to provide a prediction for the decay rate with the same precision as the measurement. The NNLO evaluation of the B -> Xs gamma decay rate has been pursued by various groups over the last decade. The project was completed to a large extent and a first estimate at this level of perturbation theory was obtained in 2006. This prediction, however, lacks important contributions from yet unknown matrix elements, that were estimated from results which are only partially known to date. In this work, we provide a framework for the systematic study of the missing matrix elements at the NNLO. As main results of this thesis, we determine fermionic corrections to the charm quark mass dependent matrix elements of four-quark operators in the effective theory at NNLO. For the first time, the full mass dependence was kept. Moreover, we evaluate both bosonic and fermionic corrections to the decay rate in the limit of vanishing charm quark mass. These findings, combined with yet unknown remaining real contributions, will help to reduce the uncertainty of the NNLO branching ratio estimate considerably. Another central topic of the present work is the development of an automatic high-precision computation of multi-loop multi-scale integrals, a crucial ingredient for the here presented results.

In this work the supersymmetric seesaw model and its effects on low-energy leptonic observables and thermal leptogenesis have been systematically investigated. Precision measurements will increase the sensitivity on lepton-flavor violating decays, particularly on Br(l_j->l_i gamma) and also on electric and magnetic dipole moments in the near future. In order to improve also the accuracy of theoretical predictions for these processes, we have performed a full one-loop calculation of the underlying supersymmetric processes taking into account the lepton masses. Since the mechanism of soft supersymmetry breaking (SSB) is completely unknown, a novel analysis beyond the often studied minimal Supergravity scenarios has been performed. This way it has been demonstrated that in the considered mSUGRA, AMSB, GMSB and gaugino mediated scenarios, the ongoing search for Br(mu->e gamma) can constrain fundamental SSB parameters and/or the seesaw parameters. On the other hand, the basic parameters of thermal leptogenesis, such as the CP asymmetry in the decays of the lightest right-handed Majorana neutrino, provide probes of the unknown complex orthogonal R-matrix of the seesaw model. / In dieser Arbeit wurde systematisch das supersymmetrische Seesaw Modell und seine Auswirkungen auf leptonische Niederenergieprozesse und thermische Leptogenese untersucht. Präzisionsmessungen werden die Messgenauigkeit in Leptonflavor verletzenden Zerfällen, insbesondere für Br(l_j->l_i gamma), sowie in elektrischen und magnetischen Dipolmomenten in naher Zukunft erhöhen. Um auch die Genauigkeit von theoretischen Vorhersagen für diese Prozesse zu steigern, wurde eine komplette Einschleifenrechnung der zugrundeliegenden supersymmetrischen Prozesse unter Berücksichtigung der Leptonmassen durchgeführt. Da der Mechanismus für "soft Supersymmetry Breaking" (SSB) unbekannt ist, wurde eine neue Studie angestellt, welche über die häufig untersuchten minimalen Supergravity Szenarien hinausgeht. Auf diese Weise konnte gezeigt werden, dass in den untersuchten Szenarien von mSUGRA, AMSB, GMSB und Gaugino Mediation die anhaltende Suche nach Br(mu->e gamma) fundamentale SSB Parameter und / oder die Seesaw Parameter einschränken kann. Auf der anderen Seite ist durch die grundlegenden Parameter von thermischer Leptogenese, wie beispielsweise die CP-Asymmetrie in den Zerfällen des leichtesten rechthändigen Majorana-Neutrinos, die Möglichkeit gegeben, die komplex-orthogonale R-Matrix des Seesaw Modells genauer zu untersuchen.

In this work, we studied in great detail how the unknown parameters of the SUSY seesaw model can be determined from measurements of observables at or below collider energies, namely rare flavor violating decays of leptons, slepton pair production processes at linear colliders and slepton mass differences. This is a challenging task as there is an intricate dependence of the observables on the unknown seesaw, light neutrino and mSUGRA parameters. In order to separate these different influences, we first considered two classes of seesaw models, namely quasi-degenerate and strongly hierarchical right-handed neutrinos. As a generalisation, we presented a method that can be used to reconstruct the high energy seesaw parameters, among them the heavy right-handed neutrino masses, from low energy observables alone. / In dieser Arbeit wurde detailliert untersucht wie die unbekannten Parameter des supersymmetrischen Seesaw-Modells durchMessung von niederenergetischen Observablen (Lepton-Flavor verletzende seltene Zerfälle der Leptonen, Slepton-Paar-Produktion an Elektron-Positron Linearbeschleunigern und Sleptonmassen-Differenzen) bestimmt werden können. Wegen des komplizierten Zusammenhangs zwischen diesen Messgrößen und den Seesaw-, Neutrino-, und SUSY-Parametern stellt dies eine große Herausforderung dar. Um die verschiedenen Einflüsse zu trennen, wurden zuerst zwei Klassen von Seesaw-Modellen betrachtet, nämlich solche die durch (quasi-)entartete und stark hierarchische rechtshändige Neutrinomassen charakterisiert sind. Zur Verallgemeinerung wurde zum Abschluss eine allgemeine Methode präsentiert, mittels der die zugrunde liegenden Hochenergie-Parameter des Seesaw-Modells allein durch niederenergetische Observable rekonstruiert werden können.

This thesis describes two pieces of work. The first is a study of the resolution of the LHCb vertex locator throughout Run 1. The second comprises analyses to measure the charm mixing and CP violation observables A_{Gamma} and y_{CP}.An estimate of the resolution of the LHCb vertex locator is required for use in the track fits. A method to measure the resolution with collision data has been developed and tested. The performance of the sub-detector throughout Run 1 of the LHC has been assessed. A significant degrading of the resolution has been seen. The effects of this on the track reconstruction has been examined with little change in the measured quantities being observed. The measurement of indirect CP violation in neutral D meson transitions has been measured through the observables A_{Gamma} and y_{CP}, using 1fb^{-1} of pp collisions with a centre of mass energy 7TeV, collected by the LHCb detector in 2011.A_{Gamma} describes the CP asymmetry of the lifetime of the D^0 decaying to a CP eigenstate (KK or pipi). The analysis documented here yields A_{Gamma} = (-0.17+-0.54)x10^{-3} when the measurements are combined. This is the world's best measurement and represented a factor of four improvement over the previous best result. The observable y_{CP} compares the effective lifetimes of the Cabibbo favoured decay D^0→Kpi and the transition to a CP eigenstate (KK or pipi). The unblinded result obtained in this document, averaged over both final states is y_{CP} = (5.61+-1.56)x10^{-3}. This result is commensurate with the world average central value within 1.25 standard deviations and has significance of 3.6 standard deviations relative to zero.

No description available.

Photoproduction has been used at colliders for decades in order to study hadronic properties of matter. The energy and luminosity of recent and future colliders allow probing also the electroweak sector through photon-photon and photon-proton interactions. At the HERA electron-proton collider, studies of the W boson production provide a stringent test of the Standard Model. At the LHC, photoproduction has to be separated from the overwhelming background of partonic interactions. A powerful ‘tagging’ technique can be introduced by adding special detectors placed far from the interaction point to detect forward scattered protons, usually present in photon-mediated processes. The HECTOR software package was written in order to provide accurate simulation of forward protons trajectories in the LHC beam-lines. These tools have been used in order to study the photoproduction of top quarks via flavor-changing neutral currents. This process is practically absent in the Standard Model, while it appears in some of its extensions. Detection of such a process would thus be an evidence for the existence of physics beyond the Standard Model.

No description available.