Measurement of BK(892)γB \to K{}^{*}(892)\gamma decays at Belle II

Collaboration
Nov 15, 2024
e-Print:
Report number:
  • Belle II Preprint 2024-029,
  • KEK Preprint 2024-31
Experiments:

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Abstract: (arXiv)
We present measurements of BK(892)γB \to K{}^{*}(892)\gamma decays using 365fb1365\,{\rm fb}^{-1} of data collected from 2019 to 2022 by the Belle~II experiment at the SuperKEKB asymmetric-energy e+ee^+e^- collider. The data sample contains (387±6)×106(387 \pm 6) \times 10^6BBB\overline{B} events. We measure branching fractions (B\mathcal{B}) and C ⁣PC\!P asymmetries (AC ⁣P\mathcal{A}_{C\!P}) for both B0K0γB^{0}\to K{}^{*0}\gamma and B+K+γB^{+}\to K{}^{*+}\gamma decays. The difference in C ⁣PC\!P asymmetries (ΔAC ⁣P\Delta \mathcal{A}_{C\!P}) and the isospin asymmetry (Δ0+\Delta_{0+}) between these neutral and charged channels are also measured. We obtain the following branching fractions and C ⁣PC\!P asymmetries: B(B0K0γ)=(4.14±0.10±0.11)×105\mathcal{B} (B^{0} \to K{}^{*0}\gamma) = (4.14 \pm 0.10 \pm 0.11 ) \times 10^{-5}, B(B+K+γ)=(4.02±0.13±0.13)×105\mathcal{B} (B^{+} \to K{}^{*+}\gamma) = (4.02 \pm 0.13 \pm 0.13 )\times 10^{-5}, AC ⁣P(B0K0γ)=(3.3±2.3±0.4)%\mathcal{A}_{C\!P} (B^{0} \to K{}^{*0}\gamma) = (-3.3 \pm 2.3 \pm 0.4 )\%, and AC ⁣P(B+K+γ)=(0.7±2.9±0.6)%\mathcal{A}_{C\!P} (B^{+} \to K{}^{*+}\gamma) = (-0.7 \pm 2.9 \pm 0.6 )\%. The measured difference in C ⁣PC\!P asymmetries is ΔAC ⁣P=(+2.6±3.8±0.7)%\Delta \mathcal{A}_{C\!P} = (+2.6 \pm 3.8 \pm 0.7 )\%, and the measured isospin asymmetry is Δ0+=(+5.0±2.0±1.5)%\Delta_{0+} = (+5.0 \pm 2.0 \pm 1.5 )\%. The first uncertainties listed are statistical and the second are systematic. These results are consistent with world-average values and theory predictions.