Recent measurements of branching fractions and $CP$ asymmetries of charmless hadronic $B$ meson decays at Belle

Abstract

Hadronic $B$ decays without a charm quark constitute a powerful probe to search for physics beyond the standard model as well as to provide constraints on $CP$ violation parameters. We report final measurements from Belle of the branching fractions and $CP$ asymmetries for the decays $B^0\to {\pi }^0{\pi }^0$ and $B^{\pm }\to K^{+}{K}^{-}{\pi }^{\pm }$. The $B^0\to {\pi }^0{\pi }^0$ measurements enable us to improve constraints on the angle ${\varphi }_2$ 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 a strong evidence for large $CP$ violation and a large increase in yield at low mass region. This result challenges conventional theoretical approaches as it requires a large enhancement in both tree and loop level diagrams in the same small region of phase-space.