Semileptonic decay Λb→Λc+τ-+ν¯τ in the covariant confined quark model

Recently there has been much interest in the tauonic semileptonic meson decays B →D +τ +ν_τ and B →D^*+τ +ν_τ , where one has found larger rates than what is predicted by the Standard Model. We analyze the corresponding semileptonic baryon decays Λ_b⁰→Λ_c⁺+τ^-+ν_{¯ τ} with particular emphasis on the lepton helicity flip and scalar contributions which vanish for zero lepton masses. We calculate the total rate, the differential decay distributions, the longitudinal and transverse polarization of the daughter baryon Λ_c⁺ and the τ lepton, and the lepton-side forward-backward asymmetries. The nonvanishing polarization of the daughter baryon Λ_c⁺ leads to hadron-side asymmetries in e.g. the decay Λ_c⁺→Λ⁰+π⁺ and azimuthal correlations between the two final-state decay planes which we specify. We provide numerical results on these observables using results of the covariant confined quark model. We find large lepton mass effects in the q² spectra and in the polarization observables.