Measurement of B → K*(892)γ decays at Belle II

A bstract We present measurements of B → K * (892) γ decays using 365 fb − 1 of data collected from 2019 to 2022 by the Belle II experiment at the SuperKEKB asymmetric-energy e + e − collider. The data sample contains (387 ± 6) × 10 6 Υ(4 S ) events. We measure branching fractions ( B ) and CP asymmetries ( ACP ) for both B 0 → K *0 γ and B + → K *+ γ decays. The difference in CP asymmetries ( Δ ACP ) and the isospin asymmetry (∆ 0+ ) between these neutral and charged channels are also measured. We obtain the following branching fractions and CP asymmetries: B(B⁰→ K*0γ )=(4.14± 0.10± 0.11)× 10⁻⁵ , B(B⁺→ K*+γ )=(4.04± 0.13-0.15+0.13)× 10⁻⁵ , ACP(B⁰→ K*0γ )=(-3.3± 2.3± 0.4)% , and ΔACP(B⁺→ K*+γ )=(-0.7± 2.9± 0.5)% . The measured difference in CP asymmetries is ΔACP=(+2.6± 3.8± 0.6)% , and the measured isospin asymmetry is ∆ 0+ = (+4.8 ± 2.0 ± 1.8)%. The first uncertainties listed are statistical and the second are systematic. These results are consistent with world-average values and theory predictions.