Singlet Heavy Fermions as the Origin of B Anomalies in Flavour Changing Neutral Currents

We show that a simple extension of the Standard Model involving the introduction of vector-like quarks and heavy neutrinos, provides an explanation of the so called B-anomalies in $b\to s\mathrm{\ell }\bar{\mathrm{\ell }}$ transitions. Vector-like quarks can explain, in the context of a discrete flavour symmetry, all the relevant characteristics of the Cabibbo-Kobayashi-Maskawa sector. It is in this framework that we study the requirements on the masses of the vector like quarks and the heavy neutrinos leading to viable models with sufficient deviations of lepton flavour universality and which simultaneously avoid too large Flavour Changing Neutral Current effects. Related predictions on $b\to d\ell\bar\ell$and$s\to d\ell\bar\ell$ transitions are also analysed in detail.