Test of Lepton Universality with b-baryon decays at LHCb

The LHCb detector at the LHC has observed a number of small deviations with respect to the Standard Model predictions in b -> sll transitions, most notably in tests of Lepton Universality comparing the couplings to muons and electrons. While a pattern is emerging, it is of uttermost importance to confirm if these deviations are present in the whole family of b -> sll decays. A first measurement of Lepton Universality with Lambda_b decays was performed by LHCb with a fraction of the collected data, with results consistent with the deviations observed in the meson sector but also with the SM predictions. It is thus critical to update this measurement with the full dataset. In particular, optimisation of the event selection and a study of the pK spectrum will enable improvements beyond the pure statistical gain from the size of the analysed data sample.