Beyond $\mathcal{R}(D^{(*)})$ with the general 2HDM-III for $b\to cτν$

Abstract

We review the parameter regions allowed by measurements of $\mathcal{R}(D^{(*)})$ and by a theoretical limit on ${\cal B}(B_{c}\toτν)$ in terms of generic scalar and pseudoscalar new physics couplings, $g_s$ and $g_p$. We then use these regions as constraints to predict the ranges for additional observables in $b\to cτν$ including the differential decay distributions $dΓ/dq^{2}$; the ratios $\mathcal{R}(J/ψ)$ and $\mathcal{R}(Λ_{c})$; and the tau-lepton polarisation in $B\to D^{(\star)}τν$, with emphasis on the CP violating normal polarisation. Finally we map the allowed regions in $g_s$ and $g_p$ into the parameters of four versions of the Yukawa couplings of the general 2HDM-III model. We find that the model is still viable but could be ruled out by a confirmation of a large $\mathcal{R}(J/ψ)$.