Resumen de Searching for new physics in semileptonic b-meson decays
In the recent years, intriguing hints of New Physics have been accumulated in semileptonic B-meson decays, mostly involving neutral-current b --> sll transitions. Different experimental collaborations at the LHC, with LHCb playing the leading role, and the Belle experiment have reported deviations from Standard Model expectations in several observables measuring these transitions. These are commonly referred to in the literature as B-anomalies. Naively, one expects some measurements in a large dataset to exhibit certain tensions with theory expectations by a few standard deviations. However, the current situation is exceptional since the aforementioned tensions form coherent patterns, in such a way that when quantified by a global fit the discrepancy with the Standard Model is over the 5sigma level.
In order to assess the significance of these anomalies and to treat them consistently, we propose a model-independent analysis based on an effective Hamiltonian encoding the dynamics of the underlying quark-level transition. This has the advantage of providing a simple systematic framework where all processes, mediated by the same transition, can be described with the same set of parameters, allowing for global fits to a large number of observables defined in several channels.
This Thesis presents our most updated analyses of b --> sll data. First, we describe the general theoretical framework used to compute the different types of observables, paying special attention to the treatment of the uncertainties involved, and then we discuss our analytical approach and the implications of the most significant results obtained from our fits.
