Measurements of branching fractions, CP and isospin asymmetries of $B\to \rho \gamma$ using 2 combined data of Belle and Belle II

Sumitted to PubDB: 2024-12-19

Category: Physics / performance paper, Visibility: Latest Version Public

Authors	Youngjoon Kwon, Shun Watanuki
Date	2025-04-24
Working group	Radiative and Electroweak Penguin
Belle II Number	BELLE2-PUB-PH-2024-040
Abstract	We present measurements of $B^{+} \to \rho^{+}\gamma$ and $B^{0} \to \rho^{0}\gamma$ decays using a combined data sample of $772 \times 10^{6} B\bar{B}$ pairs collected by the Belle experiment and $387 \times 10^{6} B\bar{B}$ pairs collected by the Belle II experiment in $e^{+}e^{−}$ collisions at the $\Upsilon(4S)$ resonance. After an optimized selection, a simultaneous fit to the Belle and Belle II data sets yields 114 ±12 $B^{+} \to \rho^{+}\gamma$ and 99±12 $B^{0} \to \rho^{0}\gamma$ decays. The measured branching fractions are $(13.1 +2.0+1.3 −1.9−1.2 ) \times 10^{−7}$ and $(7.6 ± 1.3 +1.0 −0.8 ) \times 10^{−7}$ for $B^{+} \to \rho^{+}\gamma$ and $B^{0} \to \rho^{0}\gamma$ decays, respectively, where the first uncertainty is statistical and the second is systematic. We also measure the isospin asymmetry $A_{I}(B \to \rho\gamma) = (10.9 +11.2+7.8 −11.7−7.3 )%$ and the direct CP asymmetry $A_{CP} (B^{+} \to \rho^{+}\gamma) = (−8.2 ± 15.2 +2.0 −1.3 )%$.
ArXiv	https://arxiv.org/abs/2407.08984
Journal	Phys.Rev.D
Authorship confirmation page	https://authors.belle2.org/#41
Analysis	Measurements of branching ratio, CP and Isospin asymmetry of B → ργ with Belle and Belle II