000003282 001__ 3282
000003282 005__ 20221011081739.0
000003282 037__ $$aBELLE2-CONF-PH-2022-017
000003282 041__ $$aeng
000003282 100__ $$aSvenja Granderath
000003282 245__ $$aDetermination of $|V_{ub}|$ from untagged $B^0\to\pi^- \ell^+ \nu_{\ell}$ decays using 2019-2021 Belle~II data
000003282 260__ $$a$$c2022-10-09
000003282 300__ $$amult. p
000003282 520__ $$aWe present an analysis of the charmless semileptonic decay $B^0\to\pi^- \ell^+ \nu_{\ell}$, where $\ell = e, \mu$, from 198.0 million pairs of $B\bar{B}$ mesons recorded by the Belle~II detector at the SuperKEKB electron-positron collider. The decay is reconstructed without identifying the partner $B$ meson. The partial branching fractions are measured independently for $B^0\to\pi^- e^+ \nu_{e}$ and $B^0\to\pi^- \mu^+ \nu_{\mu}$ as functions of $q^{2}$ (momentum transfer squared), using 3896 $B^0\to\pi^- e^+ \nu_{e}$ and 5466 $B^0\to\pi^- \mu^+ \nu_{\mu}$ decays. The total branching fraction is found to be $(1.426 \pm 0.056 \pm 0.125) \times 10^{-4}$ for $B^0\to\pi^- \ell^+ \nu_{\ell}$ decays, where the uncertainties are statistical and systematic, respectively. By fitting the measured partial branching fractions as functions of $q^{2}$, together with constraints on the nonperturbative hadronic contribution from lattice QCD calculations, the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element $V_{ub}$, $(3.55 \pm 0.12 \pm 0.13 \pm 0.17) \times 10^{-3}$, is extracted. Here, the first uncertainty is statistical, the second is systematic and the third is theoretical.
000003282 6531_ $$aUntagged
000003282 6531_ $$apilnu
000003282 700__ $$aFlorian Bernlochner
000003282 700__ $$aJochen Dingfelder
000003282 700__ $$aPeter Lewis
000003282 8560_ $$fgranderath@physik.uni-bonn.de
000003282 8564_ $$uhttps://docs.belle2.org/record/3282/files/BELLE2-CONF-PH-2022-017.pdf