Abstract We present a study of the rare baryonic decay b ^+ ^- Λ b → Λ τ + τ - as a probe of new physics (NP) coupled preferentially to third-generation fermions. Within the Standard Model, we evaluate the branching ratio and the lepton-flavour-universality (LFU) ratio R ^ /, R Λ τ / μ, including both perturbative and long-distance charm contributions. We show that the LFU ratio can be predicted with an uncertainty below 10%. Possible NP effects arising from lepton non-universal dynamics are analysed within an effective field theory framework motivated by the current anomalies in b c b → c τ ν and b s ^+ ^- b → s μ + μ - transitions. In this context, R ^ / R Λ τ / μ can be enhanced by several orders of magnitude, offering a clear target for upcoming searches. The implications for the related mode b pK ^+ ^- Λ b → p K τ + τ - are also briefly discussed.
Bordone et al. (Mon,) studied this question.