  With respect to large samples of $B_c$ mesons expected to be produced at CERN
Large Hadron Collider(LHC) and the large branching ratios $Br(B_{c}\to
\tau\bar\nu)$ and $Br(B_{c}\to \mu\bar\nu)$, we suggest that $B_c$ purely
leptonic decays could offer an unique probe of the standard model and its
extensions such as two Higgs doublet models and models involving supersymmetry,
and also the structure of charged weak currents.
