EPS-HEP 2017

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

7 Jul 2017, 18:15

15m

Room Mosaici-2 (Palazzo del Casinò)

Parallel Talk Flavour Physics and Fundamental Symmetries Flavour and symmetries

Speaker

Abdul Basith Kaliyar (IIT Madras)

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 $B^{\pm }\to K_S^0{K}_S^0{h}^{\pm }(h=K,\pi )$ 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 ${\varphi }_2$ 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 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 $K_S^0{K}_S^0{h}^{\pm }(h=K,\pi )$ 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 $\sin 2{\varphi }_1$ obtained in $b\to c\overline{c}s$ and $b\to sq\overline{q}$ decays.

Presentation materials

kaliyar_flavor_symmetries.pdf