Λb→Λcτν¯τdecay in the standard model and with new physics

Recently hints of lepton flavor nonuniversality emerged when the BABAR collaboration observed deviations from the standard model predictions in $R(D^{(*)})\equiv \mathcal{B}(\overline{B}\to D^{(*)+}{\tau }^{-}{\overline{\nu }}_{\tau })/\mathcal{B}(\overline{B}\to D^{(*)+}{\ell }^{-}{\overline{\nu }}_{\ell })$ ($\ell =e,\mu$). Another test of this nonuniversality can be in the semileptonic ${\mathrm{\Lambda }}_b\to {\mathrm{\Lambda }}_c\tau {\overline{\nu }}_{\tau }$ decay. In this paper we present predictions for this decay in the standard model and in the presence of new physics operators with different Lorentz structures. We present the most general fourfold angular distribution for this decay including new physics. For phenomenology, we focus on predictions for the decay rate and the differential distribution in the momentum transfer squared $q^2$. In particular, we calculate $R_{{\mathrm{\Lambda }}_b}=\frac{BR[{\mathrm{\Lambda }}_b\to {\mathrm{\Lambda }}_c\tau {\overline{\nu }}_{\tau }]}{BR[{\mathrm{\Lambda }}_b\to {\mathrm{\Lambda }}_c\ell {\overline{\nu }}_{\ell }]}$ where $\ell$ represents $\mu$ or $e$, and find the standard model prediction to be around 0.3 while the new physics operators can increase or slightly decrease this value.