PHYS. REV. D (lett.) 110, L031106 (2024)

SCIE

Search for the decay B^0 → γγ using Belle and Belle II data

Belle II Collaboration (I. Adachi, ..., N. Anh Ky, ...)

We report the result of a search for the rare decay B 0 → γγ using a combined dataset of 753 × 106 BB¯ pairs collected by the Belle experiment and 387 × 106 BB¯ pairs collected by the Belle II experiment from decays of the Υ(4S) resonance produced in e +e − collisions. A simultaneous fit to the Belle and Belle II data sets yields 11.0 +6.5 −5.5 signal events, corresponding to a 2.5σ significance. We determine the branching fraction B(B 0 → γγ) = (3.7 +2.2 −1.8 (stat) ± 0.5(syst)) × 10−8 and set a 90% credibility level upper limit of B(B 0 → γγ) < 6.4 × 10−8 .

DOI: https://doi.org/10.1103/PhysRevD.110.L031106

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