  We propose to investigate the effects of new physics in the semi-leptonic
sequential decay $\Lambda_b \to \Lambda_c (\to \Lambda \pi) \tau{\bar
\nu}_{\tau}$. Firstly, we write the general, model independent, non-covariant
expression of the differential decay width of the process. Then, we calculate
that observable according to three different types of new physics interactions,
which might explain the tension of data with the standard model predictions. We
find that some coefficients of the differential decay width are sensitive to
the kind of interaction that is assumed. The measurements that we suggest seem
to be feasible.
