Observation of time-dependent CP violation and measurement of the branching fraction of B0J/ψπ0 decays

Collaboration
Oct 11, 2024
11 pages
Published in:
  • Phys.Rev.D 111 (2025) 1, 012011
  • Published: Jan 1, 2025
e-Print:
DOI:
Report number:
  • Belle II preprint: 2024-018,
  • KEK preprint: 2024-14
Experiments:

Citations per year

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Abstract: (APS)
We present a measurement of the branching fraction and time-dependent charge-parity (CP) decay-rate asymmetries in B0J/ψπ0 decays. The data sample was collected with the Belle II detector at the SuperKEKB asymmetric e+e- collider in 2019–2022 and contains (387±6)×106BB¯ meson pairs from ϒ(4S) decays. We reconstruct 392±24 signal decays and fit the CP parameters from the distribution of the proper-decay-time difference of the two B mesons. We measure the branching fraction to be (B0J/ψπ0)=(2.00±0.12±0.09)×10-5 and the direct and mixing-induced CP asymmetries to be CCP=0.13±0.12±0.03 and SCP=-0.88±0.17±0.03, respectively, where the first uncertainties are statistical and the second are systematic. We observe mixing-induced CP violation with a significance of 5.0 standard deviations for the first time in this mode.