Measurements of B→ Kπ and B→ ππ Branching Fractions and ACP Asymmetries at Belle II

Analyses of B meson decays to charmless hadronic final states are an important part of the Belle II program. They are sensitive to effects from non-standard model physics and provide experimentally precise constraints on the weak interactions of quarks. We present recent Belle II results on branching fractions and direct $CP$-violating asymmetries of the decays B⁰ → K⁺π⁻, B⁺ → K⁺π⁰, B⁺ → K⁰π⁺, and B⁰ → K⁰π⁰, and use these to test the standard model through an isospin-based sum rule. In addition, we measure the branching fraction and direct $CP$ asymmetry of the decay B⁺ → π⁺π⁰ and the branching fraction of the decay B⁰ → π⁺π⁻, which contribute towards the determination of the CKM angle φ₂. The data are collected with the Belle II detector from the SuperKEKB asymmetric-energy e⁺e⁻ collider, consisting of 387 × 10⁶ Υ(4S)→ BB̄ events. We obtain -0.03 ± 0.13 ± 0.04 for the sum rule, in agreement with the standard model expectation of zero and with a precision comparable to the best existing determinations.