Scalar contributions to b→c(u)τν transitions

Abstract

We perform a comprehensive analysis of scalar contributions in b c transitions including the latest measurements of R(D ( * ) ), the q 2 differential distributions in B D ( * ) , the polarization asymmetry for B D * , and the bound derived from the total width of the B c meson. We find that scalar contributions with the simultaneous presence of both left-and right-handed couplings to quarks can explain the available data, specifically R(D ( * ) ) together with the measured differential distributions. However, the constraints from the total B c width present a slight tension with the current data on B D * in this scenario, preferring smaller values for R(D * ). We discuss possibilities to disentangle scalar new physics from other new-physics scenarios like the presence of only a left-handed vector current, via additional observables in B D ( * ) decays or additional decay modes like the baryonic b c and the inclusive B X c decays. We also analyze scalar contributions in b u transitions, including the latest measurements of B , providing predictions for b p and B decays. The potential complementarity between the b u and b c sectors is finally investigated once assumptions about the flavour structure of the underlying theory are made.