Search for the suppressed and yet unobserved B -> pi e+ e- decay using LHCb data and machine learning techniques

The LHCb detector is one of the main experiments at the LHC at CERN, specialized on the study of CP breaking and rare decays of b hadrons. Semileptonic transitions of a b quark to an s quark and two leptons (b -> sll) have been intensively studied during the last decade, with some hints of potential new physics effects. The analogous transitions with a d quark in the final state (b -> dll) are more suppressed in the Standard Model and thus highly sensitive to potential new physics effects, at even higher scales. There transitions are however largely unexplored due to the experimental challenges they involve. Only two b -> dll decays with muons and none with electrons in the final state have been observed to date. The large data sample collected by the LHCb experiment should enable the observation of these decays, provided a powerful discriminating power with respect other transitions is achieved in the event selection. The goal of this project is to search for the b -> de+e- transition B -> pi e+e-, using the data from the LHCb experiment and applying machine learning techniques to suppress the large background affecting this final state. This is the first step towards measuring the properties b -> dll transitions, most notably lepton flavour universality ratios, which provide a stringent test of the Standard Model.