Measurement of the photon-energy spectrum in inclusive B-> X_s gamma decays identified using hadronic decays of the recoil B meson in 2019–2021 Belle II data

Sumitted to PubDB: 2023-02-27

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Authors	Arthur Bolz, Lu Cao, Markus Röhrken, Henrikas Svidras, Kerstin Tackmann
Date	Oct. 20, 2022
Belle II Number	BELLE2-CONF-PH-2022-018
Abstract	We measure the photon-energy spectrum in radiative bottom-meson ($B$) decays into inclusive final states involving a strange hadron and a photon. We use SuperKEKB electron-positron collisions corresponding to $189$/fb of integrated luminosity collected at the $\Upsilon(4S)$ resonance by the Belle II experiment. The partner $B$ candidates are fully reconstructed using a large number of hadronic channels. The $B\rightarrow X_s \gamma$ partial branching fractions are measured as a function of photon energy in the signal $B$ meson rest frame in eight bins above 1.8 GeV. The background-subtracted signal yield for this photon energy region is $343 \pm 122$ events. Integrated branching fractions for three photon energy thresholds of $1.8$~GeV, $2.0$~GeV, and $2.1$~GeV are also reported, and found to be in agreement with world averages.