Probing lepton flavour universality with Λ b decays to τ ⁺τ ⁻ final states

We present a study of the rare baryonic decay Λ b → Λ τ ⁺ τ ⁻ 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 RΛτ /μ, 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 → cτ ν b → c τ ν and b → sμ ⁺μ ⁻ b → s μ + μ - transitions. In this context, RΛτ /μ 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 Λ b → pKτ ⁺τ ⁻ Λ b → p K τ + τ - are also briefly discussed.