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Theoretical Physycs Group at Scuola Normale Superiore
Piazza dei Cavalieri, 7
56100 Pisa PI - Italy
ph. +39 050 509203
ph. +39 050 509111

Dario Buttazzo (Zurich U. & INFN, Pisa)

On the breaking of Lepton Flavour Universality in B meson decays

Abstract
Several different experiments show evidences of Lepton Flavour Universality violation in semileptonic B meson decays, both in charged and neutral currents. These anomalies can be interpreted in terms of new short-distance interactions that involve mainly the third generation of fermions. I will discuss the present status of the anomalies, and their connection to other low- and high-energy observables, adopting an Effective Field Theory approach based on a U(2) flavour symmetry. I will then extend the analysis to a few simplified UV completions with different types of mediator, discussing the main issues that have to be faced in each case. A few models emerge, which look capable of accommodating both charged- and neutral-current anomalies, consistently with all the experimental bounds, and without considerable fine-tunings.