Measurement of CKM Matrix Element $|V_{cb}|$ from $\bar{B} \to D^{*+} \ell^{-} \bar{\nu}_\ell$

We present a new measurement of the CKM matrix element $|V_{cb}|$ from $ B^{0} rightarrow D^{*}ell nu$ decays, reconstructed with full Belle data set ($711 , rm fb^{-1}$). Two form factor parameterisations, based on work by the CLN and BGL groups, are used to extract the product $mathcal{F}(1)eta_{rm EW}|V_{cb}|$ and the decay form factors, where $mathcal{F}(1)$ is the factor normalisation and $eta_{rm EW}$ is a small electroweak correction. In the CLN parameterisation we find $mathcal{F}(1)eta_{rm EW}|V_{cb}| = (35.06 pm 0.15 pm 0.54) times 10^{-3}$, $rho^{2}=1.106 pm 0.031 pm 0.007$, $R_{1}(1)=1.229 pm 0.028 pm 0.009$, $R_{2}(1)=0.852 pm 0.021 pm 0.006$. In the BGL parameterisation we find $mathcal{F}(1)eta_{rm EW}|V_{cb}|= 38.73 pm 0.25 pm 0.60$, which is higher but consistent with the determination from inclusive semileptonic $B$ decays when correcting for $mathcal{F}(1)eta_{rm EW}$. This is the most precise measurement of $mathcal{F}(1)eta_{rm EW}|V_{cb}|$ and form factors that has ever been carried out, and the first direct study of the BGL form factor parameterisation in an experimental measurement.