Measurements of $\mathbf{B}\to \mathbf{K\pi }$ and $\mathbf{B}\to \mathbf{\pi \pi }$ Branching Fractions and ${\mathcal{A}}_{\mathbf{CP}}$ Asymmetries at Belle II

Abstract

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 $B^0\to K^{+}{\pi }^{-}$, $B^{+}\to K^{+}{\pi }^0$, $B^{+}\to K^0{\pi }^{+}$, and $B^0\to K^0{\pi }^0$, 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 $B^{+}\to {\pi }^{+}{\pi }^0$ and the branching fraction of the decay $B^0\to {\pi }^{+}{\pi }^{-}$, which contribute towards the determination of the CKM angle ${\varphi }_2$. The data are collected with the Belle II detector from the SuperKEKB asymmetric-energy $e^{+}{e}^{-}$ collider, consisting of $387\times 10^6$ ${\rm Y}(4S)\to B\bar{B}$ events. We obtain $-0.03\pm 0.13\pm 0.04$ for the sum rule, in agreement with the standard model expectation of zero and with a precision comparable to the best existing determinations.

arXiv commentcontribution to the 2024 Electroweak session of the 58th Rencontres de Moriond