$|V_{cb}|$ determinations from $\bar{B} \to D^{(*)} \ell \bar\nu$ decays within the SM and beyond

Abstract

We investigate the $|V_{cb}|$ determinations from exclusive semi-leptonic $\bar{B} \to D^{(*)}\ell\bar\nu$ decays, together with comprehensive fit analyses of the $\bar{B} \to D^{(*)}$ transition form-factors, by taking into account recent updates of experimental distribution data and theoretical evaluations. Several commonly adopted form-factor parameterizations, including BSZ, BGL and HQET, have been considered under different fit scenarios. We compare the fitted values and study how the $|V_{cb}|$ determinations depend on the form-factor parameterizations and on the treatment of the experimental inputs. In particular, we reproduce the official PDG average of $|V_{cb}|$ with the BGL parameterization, while the HQET parameterization tends to give a smaller value of $|V_{cb}|$. We also consider new-physics effects that can contribute to $\bar{B} \to D^{(*)}\ell\bar\nu$, and examine whether non-zero new-physics contributions are still allowed by the current data.