$\bar{B}\rightarrow D^{(\ast)}τ\barν$ excesses in ALRSM constrained from $B$, $D$ decays and $D^{0}-\bar{D}^{0}$ mixing

Abstract

Recent experimental results from the LHCb, BaBar and Belle collaborations on the semitauonic decays of $B$ meson, $\bar{B}\rightarrow D^{(\ast)}τ\barν$, 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 $\bar{B}\rightarrow D τ\barν$ and $\bar{B}\rightarrow D^{(\ast)}τ\barν$ via the exchange of scalar leptoquarks. We study the leptonic decays $D_{s}^{+} \rightarrow τ^{+} \barν$, $B^{+}\rightarrow τ^{+} \barν$, $D^{+}\rightarrow τ^{+} \barν$ 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.

10 pages, 10 figures, minor refinements, all results unchanged, new references added