Measurement of the branching fraction and $CP$ asymmetry in $B^0\to {\pi }^0{\pi }^0$ decays, and an improved constraint on ${\varphi }_2$

Abstract

We measure the branching fraction and $CP$ violation asymmetry in the decay $B^0\to {\pi }^0{\pi }^0$, using a data sample of $752\times 10^6$ $B\bar{B}$ pairs collected at the ${\rm Y}(4S)$ resonance with the Belle detector at the KEKB $e^{+}{e}^{-}$ collider. The obtained branching fraction and direct $CP$ asymmetry are $\mathcal{B}(B\to {\pi }^0{\pi }^0)=[1.31\pm 0.19\text{(stat.)}\pm 0.19\text{(syst.)}]\times 10^{-6}$ and $A_{CP}=+0.14\pm 0.36\text{(stat.)}\pm 0.10\text{(syst.)},$ respectively. The signal significance, including the systematic uncertainty, is 6.4 standard deviations. We combine these results with Belle's earlier measurements of $B^0\to {\pi }^{+}{\pi }^{-}$ and $B^{\pm }\to {\pi }^{\pm }{\pi }^0$ to exclude the $CP$-violating parameter ${\varphi }_2$ from the range $15.5^{\circ }<{\varphi }_2<75.0^{\circ }$ at 95\% confidence level.

arXiv comment8 pages, 2 figures

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Cited by in corpus (5)

• Averages of $b$-hadron, $c$-hadron, and $\tau$-lepton properties as of 2021
• Revisiting Final State Interaction in Charmless $B_q\to PP$ Decays
• Measurement of the branching fraction and $CP$ asymmetry of $B^0\to {\pi }^0{\pi }^0$ decays using $198\times 10^6$ $B\overline{B}$ pairs in Belle II data
• Search for the decay $B_s^0\to {\pi }^0{\pi }^0$ at Belle
• Rescaling the isospin triangle argument for constraining ${\varphi }_2$ ($\alpha$): consolidating Belle II and a potential path forward for LHCb