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

Tags: Data Production

Principal Authors Youngjoon Kwon, Shun Watanuki, Alan Schwartz
Date 2025-04-24
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 \pm 12 $B^{+} \to \rho^{+}\gamma$ and 99\pm 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 $(7.6 \pm 1.3 +1.0 -0.8 ) \times 10^{-7}$ 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 $A_{CP} (B^{+} \to \rho^{+}\gamma) = (-8.2 \pm 15.2 +2.0 -1.3 )%$.
ArXiv https://arxiv.org/abs/2407.08984
Inspire https://inspirehep.net/literature/2807332
DOI 10.1103/PhysRevD.111.L071103
Reference Phys.Rev.D 111, L071103 (2025)
Bibtex 
@article{Belle:2024qhe,
    author = "Adachi, I. and others",
    collaboration = "Belle, Belle-II",
    title = "{Measurement of branching fractions, CP asymmetry, and isospin asymmetry for B{\textrightarrow}{\ensuremath{\rho}}{\ensuremath{\gamma}} decays using Belle and Belle II data}",
    eprint = "2407.08984",
    archivePrefix = "arXiv",
    primaryClass = "hep-ex",
    reportNumber = "Belle II Preprint 2023-019; KEK Preprint 2023-37; UCHEP-24-04, Belle II Preprint 2023-019; KEK Preprint 2023-37",
    doi = "10.1103/PhysRevD.111.L071103",
    journal = "Phys. Rev. D",
    volume = "111",
    number = "7",
    pages = "L071103",
    year = "2025"
}
Journal Phys.Rev.D

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