Speaker
Description
Hadronic $B$ decays without a charm quark constitute a powerful probe to search for
physics beyond the standard model as well as provide constraints of $CP$-violation
parameters. We report the final measurements from Belle of the branching fraction
and $CP$ asymmetry for the decays $B^{0}\to \pi^{0}\pi^{0}$, $B^{\pm}\to
K^{+}K^{-}\pi^{\pm}$ and preliminary results for $B^\pm\to K^{0}_{S}K^{0}_{S}h^{\pm} (h =K,\pi)$ and $B^{\pm}\to \pi^{+}\pi^{-}\pi^{\pm}$. All investigations employ the full data sample delivered by the KEKB $e^{+}e^{-}$ collider. The $B^{0}\to \pi^{0}\pi^{0}$ measurements enable improved constraints on the angle $\phi_{2}$ of the CKM unitarity triangle. For $B^{\pm}\to K^{+}K^{-}\pi^{\pm}$ we measure $CP$ asymmetry as a function of the invariant-mass of the $K^{+}K^{-}$ system, where we find strong evidence for large direct $CP$-violation as well as a large increase in yield at low mass. This measurement challenges conventional theoretical approaches since the result requires a large enhancement in both tree and loop diagrams in the same small region of phase-space. The three-body decay final states $\pi^{+}\pi^{-}\pi^{\pm}$ and $K^{0}_{S}K^{0}_{S}h^{\pm} (h=K,\pi)$ proceed mostly via flavor-changing neutral currents and are thus sensitive to new physics via enhanced $CP$-asymmetry due to interference from non-SM amplitudes in loops. The final measurement plays an important role in understanding the $B$ decay dynamics and improving the deviation boundary of $\sin 2\phi_1$ obtained in $b\to c\bar{c}s$ and $b\to sq\bar{q}$ decays.
| Experimental Collaboration | Belle |
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