Measurement of Branching Fractions and Direct CP Asymmetries for $B^{+} \to K^{0}\pi^{+}$, $B^{+} \to K^{+}\pi^{0}$, and $B^{+} \to \pi^{+}\pi^{0}$ Decays at Belle II

Sumitted to PubDB: 2026-01-30

Category: Phd Thesis

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Principal Authors	Justin Skorupa
Date	2025-10-01
Belle II Number	BELLE2-PTHESIS-2026-002
Abstract	We present measurements of branching fractions and direct CP asymmetries for $B^{+} \to K^{0}\pi^{+}$, $B^{+} \to K^{+}\pi^{0}$, and $B^{+} \to \pi^{+}\pi^{0}$ decays. The analysis uses a data sample containing 387 million bottom-antibottom meson pairs produced in $e^{+}e^{-}$ collisions at the $\Upsilon(4S)$ resonance by the SuperKEKB collider and recorded with the Belle II detector. The measured branching fractions are: $B^{+} \to K^{0}\pi^{+}$ : $(24.37 \pm 0.71 \pm 0.86)\times 10^{-6}$, $B^{+} \to K^{+}\pi^{0}$ : $(13.93 \pm 0.38 \pm 0.71)\times 10^{-6}$, and $B^{+} \to \pi^{+}\pi^{0}$ : $(5.10 \pm 0.29 \pm 0.27)\times 10^{-6}$. The corresponding direct CP asymmetries are: $B^{+} \to K^{0}\pi^{+}$ : $0.046 \pm 0.029 \pm 0.007$, $B^{+} \to K^{+}\pi^{0}$ : $0.013 \pm 0.027 \pm 0.005$, and $B^{+} \to \pi^{+}\pi^{0}$ : $-0.081 \pm 0.054 \pm 0.008$, where the first uncertainties are statistical and the second are systematic. To test the standard model, we combine our results with Belle II measurements for $B^{0} \to K^{+}\pi^{-}$ and $B^{0} \to K^{0}\pi^{0}$ conducted on the same data set to evaluate an isospin-based sum rule. We find $-0.03 \pm 0.13 \pm 0.04$ for the sum rule, consistent with the standard model expectation of zero.
Institute	MPP