  Motivated by the anomalies present in $b \to u$ and $b \to c$ semileptonic
decays, we study the corresponding $B_s \to (K,K^*) \tau \nu$ and $B \to \pi
\tau \nu$ decays within an effective field theory formalism. Our analysis is
based on a strict model dependent assumption, i.e., we assume that $b \to u$
and $b \to c$ transition decays exhibit similar new physics pattern. We give
prediction of various observables such as the branching fraction, ratio of
branching ratio, lepton side forward-backward asymmetry, longitudinal
polarization fraction of the charged lepton and convexity parameter in the
standard model and in the presence of vector type new physics couplings.
