Extraction of $|V_{cb}|$ from $B\to D^{(*)}\ell\nu_\ell$ and the Standard Model predictions of $R(D^{(*)})$

Abstract

We extract $|V_{cb}|$ from the available data in the decay $B \to D^{(*)}\ell\nu_{\ell}$. Our analysis uses the $q^2(w)$ binned differential decay rates in different subsamples of $B\to D\ell\nu_\ell$ ($\ell = e, \mu$), while for the decay $B\to D^*\ell\nu_\ell$, the unfolded binned differential decay rates of four kinematic variables including the $q^2$ bins have been used. In the CLN and BGL parameterizations of the form factors, the combined fit to all the available data along with their correlations yields $|V_{cb}| = (39.77 \pm 0.89)\times 10^{-3}$ and $(40.90 \pm 0.94)\times 10^{-3}$ respectively. In these fits, we have used the inputs from lattice and light cone sum rule (LCSR) along with the data. Using our fit results and the HQET relations (with the known corrections included) amongst the form factors, and parameterizing the unknown higher order corrections (in the ratios of HQET form factors) with a conservative estimate of the normalizing parameters, we obtain $R(D^{*}) = 0.259 \pm 0.006$ (CLN) and $R(D^*) = 0.257 \pm 0.005$ (BGL).