000002179 001__ 2179
000002179 005__ 20201207142907.0
000002179 037__ $$aBELLE2-CONF-PROC-2020-021
000002179 041__ $$aeng
000002179 100__ $$aWilliam Sutcliffe
000002179 245__ $$aEarly results from Full Event Interpretation at Belle II
000002179 260__ $$a$$c2020-11-07
000002179 300__ $$a6
000002179 520__ $$aFull Event Interpretation is an algorithm for tag-side $B$ meson reconstruction at Belle II. The algorithm employs a hierarchical reconstruction of exclusive decay chains of $B$ mesons, with multivariate classifiers utilised to identify each unique sub-decay channel. Here, calibration factors are derived for hadronic tag-side $B$ decays by measuring $B \rightarrow X\ell \nu$ decays. For a very loose selection on the tag-side $B$ multivariate classifier, the calibration factors are $0.65 \pm 0.02$ and $0.83 \pm 0.03$ for tag-side $B^{+}$ and $B^{0}$ mesons, respectively. The calibrated hadronic tag-side decay modes are used to measure the branching fractions $\mathcal{B}(B^{0} \rightarrow D^{*+} \ell^{-} \bar{\nu}_{\ell}) = (4.45 \pm 0.41 ({\rm stat}) \pm 0.27 ({\rm sys}) \pm 0.45 (\pi_{\rm s})) \times 10^{-2}$ and $\mathcal{B}(B^{0} \rightarrow \pi^{+} \ell^{-} \bar{\nu}_{\ell}) = (1.62 \pm 0.42 ({\rm stat}) \pm 0.07 ({\rm sys})) \times 10^{-4}$ in $34.6$ fb$^{-1}$ of Belle II data. 
000002179 8560_ $$fwilliam.sutcliffe@desy.de
000002179 8564_ $$uhttps://docs.belle2.org/record/2179/files/BELLE2-CONF-PROC-2020-021.pdf