Recent experimental results from the LHCb, BaBar and Belle collaborations on the semitauonic decays of $B$ meson, $\bar{ B}\rightarrow D^{ (\ast)}\tau \bar{ \nu}$, showing a significant deviation from the Standard Model (SM), hint towards a new physics scenario beyond the SM. In this work, we show that these enhanced decay rates can be explained within the framework of $E_{ 6}$ motivated Alternative Left-Right Symmetric Model (ALRSM), which has been successful in explaining the recent CMS excesses and has the feature of accommodating high scale leptogenesis. The R-parity conserving couplings in ALRSM can contribute universally to both $\bar{ B}\rightarrow D \tau \bar{ \nu}$ and $\bar{ B}\rightarrow D^{ (\ast)}\tau \bar{ \nu}$ via the exchange of scalar leptoquarks. We study the leptonic decays $D_{ s}^{ +} \rightarrow \tau^{ +} \bar{ \nu}$, $B^{ +}\rightarrow \tau^{ +} \bar{ \nu}$, $D^{ +}\rightarrow \tau^{ +} \bar{ \nu}$ and $D^{ 0}$-$\bar{ D}^{ 0}$ mixing to constrain the couplings involved in explaining the enhanced $B$ decay rates and we find that ALRSM can explain the current experimental data on $\mathcal{ R}(D^{ (\ast)})$ quite well while satisfying these constraints.
Categories: hep-ph hep-ex