Investigation of Λ b → Λ c ℓ − ν ℓ ¯ decays in the perturbative QCD approach

We investigate the semileptonic decays Λ b → Λ c ℓ − ν ¯ ℓ (with ℓ = e , μ , τ ) within the framework of perturbative QCD. The six independent Λ b → Λ c transition form factors are first calculated in the low- q 2 region using the k T factorization approach. These are then extrapolated to the full physical q 2 range via the model-independent z expansion, incorporating recent lattice QCD results at high q 2 . Based on the obtained form factors, we compute the branching fractions of Λ b → Λ c ℓ − ν ¯ ℓ decays. Our prediction for the lepton flavor universality ratio, R Λ c = 0.2 9 − 0.11 + 0.12 , is slightly larger than the latest experimental measurement. In addition, we analyze several angular observables, including forward-backward asymmetries, lepton-side convexity parameters, and polarization asymmetries. These results offer valuable theoretical input for current and future experimental investigations of semileptonic heavy-to-heavy baryon transitions.