2024/07/12 by Belle II Collaboration, Adachi, I., Adamczyk, K. +407
#FOS: Physical sciences #High Energy Physics - Experiment (hep-ex)
paper · doi:10.48550/arxiv.2407.08984
We present measurements of B+→ρ+γ and B0→ρ0γ decays using a combined data sample of 772 × 106 BB pairs collected by the Belle experiment and 387× 106 BB pairs collected by the Belle II experiment in e+e- collisions at the Υ(4S) resonance. After an optimized selection, a simultaneous fit to the Belle and Belle II data sets yields 114± 12 B+→ρ+γ and 99± 12 B0→ρ0γ decays. The measured branching fractions are (13.1+2.0 +1.3-1.9 -1.2)× 10-7 and (7.5± 1.3+1.0-0.8)× 10-7 for B+→ρ+γ and B0→ρ0γ decays, respectively, where the first uncertainty is statistical and the second is systematic. We also measure the isospin asymmetry A\rm I(B→ργ)=(10.9+11.2 +7.8-11.7 -7.3)% and the direct CP asymmetry ACP(B+→ρ+γ)=(-8.2± 15.2+1.6-1.2)%.