Diagrammatic Analysis of Charmless Three-Body B Decays

We express the amplitudes for charmless three-body B decays in terms of diagrams. In addition, we show how to use Dalitz-plot analyses to obtain decay amplitudes which are symmetric or antisymmetric under the exchange of two of the final-state particles. When annihilation-type diagrams are neglected, as in two-body decays, many of the exact, purely isospin-based results are modified, leading to new tests of the standard model (SM). Some of the tests can be performed now, and we find that present data agree with the predictions of the SM. Furthermore, contrary to what was thought previously, it is possible to cleanly extract weak-phase information from three-body decays, and we discuss methods for B -> K pi pi, K K Kbar, K Kbar pi and pi pi pi.Comment: 30 pages, 10 figures, reference updated, sentences added regarding indirect CP violation and CP of the final state. Significant text added describing how to obtain symmetric/antisymmetric decay amplitudes, results of the comparison of the predictions of the SM with present data for several decays, and the momentum dependence of the diagram

Analyse diagrammatique des désintégrations de type B vers PPP sans quarks charmés

Ce mémoire présente l’application de la méthode de décomposition en termes de diagrammes aux désintégrations de mésons B vers trois mésons de type pseudos- calaire ne comportant pas de quarks charmés. La décomposition diagrammatique des désintégrations de types B → Kππ, B → KKK ̄, B → KK ̄π et B → πππ est effectuée de façon systématique. Il est démontré que lorsque l’on néglige les dia- grammes d’échanges et d’annihilations, dont les contributions sont estimées être petites, de nouvelles relations apparaissent entre les amplitudes. Ces relations sont de nouveaux tests du modèle standard qui ne peuvent être obtenus que par la méthode diagrammatique. Lorsque les données nécessaires sont disponibles, nous vérifions ces relations et obtenons un bon accord avec les données expérimentales. Nous démontrons également qu’il est possible d’utiliser le secteur B → Kππ pour mesurer la phase faible γ avec une incertitude théorique que nous estimons être de l’ordre de 5%. Les autres secteurs de désintégrations ne permettent d’extraire des phases faibles que si l’on invoque des approximations de précisions inconnues.This Master’s thesis presents the application of the method of decomposition in terms of diagrams to the charmless decays of B mesons to three pseudoscalar particles. We systematically apply the diagrammatic method to the decays B → Kππ, B → KKK ̄, B → KK ̄π and B → πππ. It is shown that when we neglect exchange and annihilation diagrams, whose contributions have been estimated to be small, new relations appear between the decay amplitudes. These relations constitute new tests of the standard model that can only be obtained through the diagrammatic method. When the necessary data is available, we verify these relations and obtain a good agreement with the experimental results. We also show that it is possible use observables in the B → Kππ sector to measure the weak phase γ with a theoretical uncertainty of the order of 5%. Other decay sectors can only allow the extraction of weak phases through the use of approximations of unknown precision

Phenomenology of ELDER dark matter

Abstract We explore the phenomenology of Elastically Decoupling Relic (ELDER) dark matter. ELDER is a thermal relic whose present density is determined primarily by the cross-section of its elastic scattering off Standard Model (SM) particles. Assuming that this scattering is mediated by a kinetically mixed dark photon, we argue that the ELDER scenario makes robust predictions for electron-recoil direct-detection experiments, as well as for dark photon searches. These predictions are independent of the details of interactions within the dark sector. Together with the closely related Strongly-Interacting Massive Particle (SIMP) scenario, the ELDER predictions provide a physically motivated, well-defined target region, which will be almost entirely accessible to the next generation of searches for sub-GeV dark matter and dark photons. We provide useful analytic approximations for various quantities of interest in the ELDER scenario, and discuss two simple renormalizable toy models which incorporate the required strong number-changing interactions among the ELDERs, as well as explicitly implement the coupling to electrons via the dark photon portal