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Description
Charmless hadronic B decays constitute a powerful probe to search for new physics beyond the standard model and provide constraints of various CP violation parameters. We report the final measurements from Belle of the branching fraction and CP asymmetry for a variety of charmless decays -- $B^0 \to \pi^0\pi^0$, $B^+ \to K^+ K^- \pi^+$, $B\to \phi \phi K$, and $B^+ \to K_S^0 K_S^0 h^+$ $(h=K,\pi)$ -- as well as a search for the $B^0 \to \eta\eta$ decay. All investigations employ the full dataset at $\Upsilon(4S)$ delivered by the KEKB $e^+ e^-$ collider. The $B^0 \to \pi^0 \pi^0$ measurement enables improved constraints on the CKM unitarity triangle $\phi_2$. For $B^+ \to K^+ K^- \pi^+$ we measure CP asymmetry as a function of the invariant mass of the $K^+ K^-$ system, where LHCb has earlier reported an unexpectedly strong enhancement at low mass. The three-body decays $B^+ \to K_S^0 K_S^0 h^+$ $(h=K,\pi)$ and $B\to \phi \phi K$ both proceed predominantly via flavor-changin!
g neutral current transitions and hence are sensitive to potential new physics effects. The $B^0 \to \eta\eta$ decays could play an important role in understanding the $B$ decay dynamics and improving the deviation boundary of $\sin 2\phi_1$ measured in $b\to s c\bar{c}$ and $b\to s q\bar{q}$ decays.
Charmless $B_s$ decays are studied using a data sample of 121 fb−1 collected at the Υ(10860) resonance ($\sqrt{s} = 10.87$ GeV) at Belle. We present the branching fraction of $B_s \to K^0 \bar{K}^0$, which is the first observation of a charmless two-body $B_s$ decays involving only neutral hadrons in the final state. Also presented is the first search for $B_s \to \eta\eta$ decay.
