We would like to thank S. Shivashankara for pointing out the first two typos.

Recently there has been much interest in the tauonic semileptonic meson decays B → D + τ + ντ and B → D * + τ + ντ , where one has found larger rates than what is predicted by the Standard Model. We analyze the corresponding semileptonic baryon decays Λ 0 b → Λ + c + τ − +ντ 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 forwardbackward asymmetries. The nonvanishing polarization of the daughter baryon Λ + c leads to hadronside asymmetries in e.g. the decay Λ + c → Λ 0 + 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 q 2 spectra and in the polarization observables. PACS numbers: 12.39.Ki,13.30.Eg,14.20.Jn,14.20.Mr Keywords: relativistic quark model, light and heavy baryons, decay rates and asymmetries 2 I IntroductionRecently there has been much discussion about tensions and discrepancies in some of the experimental results on leptonic, semileptonic and rare decays involving µ and τ leptons with the predictions of the Standard Model (SM). Among these are the tauonic B decaysB → τν τ ,B → D τν τ andB → D * τν τ and the muonic decays B → K * µ + µ − and Br[B → Kµ + µ − ]/Br[B → Ke + e − ]. The situation has been nicely summarized in Refs. [1][2][3][4]. The biggest discrepancies with SM predictions have been reported by the BaBar [5] and the Belle collaborations [6,7] for the decays B → D ( * ) τν τ . The discrepancy with the SM results has been summarized in Ref. [8] by comparing the SM predictions for the ratioswith the experimental results combined from Babar and Belle. The SM predictions were found to be smaller than the measurements by almost 3.5 σ:This observation has inspired a number of searches for new physics beyond the SM (BSM) in charged current interactions. These include the addition of new effective vector, scalar and tensor interactions in addition to the standard V − A interaction. Details can be found in the recent literature on this subject (see, e.g. Refs. [8][9][10][11][12][13][14][15][16][17][18][19][20][21]). Motivated by the discrepancy between theory and experiment in the meson sector, we analyze the corresponding semileptonic baryon decays Λ 0 b → Λ + c + τ − +ν τ within the SM with particular emphasis on the lepton helicity flip contributions which vanish for zero lepton masses. We collect the necessary tools to analyze the semileptonic decay Λ 0 b → Λ + c + ℓ − +ν ℓ (ℓ = e, µ, τ ) as well as the corresponding cascade decay Λ 0 b → Λ + c (→ Λ 0 + π + ) + ℓ − +ν ℓ . As in Refs. [22][23][24], we describe the semileptonic decays using the helicity formalism which allows one to include lepton mass and polarization effects without much additional effort.We calculate ...

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We analyze the tauonic semileptonic baryon decays Λ 0 b → Λ + c + τ − +ντ with particular emphasis on the lepton helicity flip contributions which vanish for zero lepton masses. We calculate the total rate, differential decay distributions, the longitudinal and transverse polarization components of the Λ

No abstract