TESTS OF LEPTON FLAVOUR UNIVERSALITY IN \(b\to c\ell \nu \) DECAYS AT THE LHCb EXPERIMENT*

Several measurements, aimed at testing the lepton flavour universality hypothesis, have been performed by the B-physics experiments which exploit both neutral current (b $\to$ s$\ell \ell$) and charged current (b $\to$ c$\ell \nu$) decays. The combination of the measurements carried out in the charged current sector shows possible hints of deviations with respect to the Standard Model predictions. This document reports the analyses, performed by the LHCb experiment, of semi-tauonic decays with both leptonic and the hadronic decays of the lepton.