Measurement of $b\to u\mathrm{\ell }\nu$ at Belle II

The semileptonic $B$ meson decays of the type $B\to X_u\mathrm{\ell }\nu$ are important for measuring the magnitude of the CKM matrix element $V_{ub}$. Recent measurements of inclusive $B\to X_{u}e{\nu }_e$ and hadronically tagged $B^0\to {\pi }^{-}{\mathrm{\ell }}^{+}\nu$ from the Belle II experiment are presented. The results are obtained using the data collected at Belle II between March 2019 and March 2020, with a total integrated luminosity of 37.8 ${\mathrm{f}\mathrm{b}}^{-1}$. These preliminary measurements are used to validate the detector and reconstruction software performance. The measured preliminary branching fraction of $B^0\to {\pi }^{-}{\mathrm{\ell }}^{+}\nu$ decays is $(1.58 \pm 0.43_{$\text{stat}$} \pm 0.07_{$\text{sys}$})\cdot 10^{-4}$, which is in agreement with the world average, $(1.50\pm 0.06)\cdot {10}^{-4}$.