$\Lambda_b \to \Lambda_c \tau \bar{\nu}_{\tau}$ Decay in the Standard Model and with New Physics

Understand

Recently hints of lepton flavor non-universality emerged when the BaBar Collaboration observed deviations from the standard model predictions in $R(D^{(*)}) \equiv {\cal B}({\bar B} \to D^{(*)+} \tau^- {\bar\nu}_\tau) / {\cal B}({\bar B} \to D^{(*)+} \ell^- {\bar\nu}_\ell)$ ($\ell =e,\mu$).

• Another test of this non-universality can be in the semi leptonic $\Lambda_{b}\to\Lambda_{c}\tau\bar{\nu}_{\tau}$ decay.
• In this work 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 four-fold angular distribution for this decay including new physics.