Search for flavour anomalies in the quark sector at the LHCb experiment

Abstract

In this thesis a time-integrated and flavour-untagged amplitude analysis is performed to four-body decays of the neutral mesons Bs and Bd, using data collected by the LHCb experiment in Run 1 and Run 2. Observables to be measured include the investigation of an anomaly in the polarisation of vector resonances when they arise from decays of Bs and Bd mesons, which seems to point to a break in the universality of the gluonic couplings to the different quark generations in the Standard Model. These decay channels, besides being a reference for the study of CP-violating and T-violating observables in charmless b-quark decays, have recently been tagged by theoretical groups as the source of a flavour anomaly, which might be connected to other flavour anomalies presented by LHCb in semi-leptonic channels. The project includes several innovations, both phenomenological and experimental. The formalism that is used to describe intermediate states considers Lorentz invariant partial waves in the basis of angular momentum, which is more fundamental in quantum mechanics and allow to associate centrifugal barrier factors.