Results on $\phi_2$ from Belle

TL;DR

This paper summarizes Belle experiment measurements related to the CKM angle φ2, including CP asymmetries and branching fractions in B meson decays, using a large data sample to constrain the angle through isospin analysis.

Contribution

It provides new measurements of CP asymmetries and branching fractions in B decays, improving constraints on the CKM angle φ2 using isospin analysis.

Findings

Measured CP asymmetries in B→π+π− decays.

Determined branching fractions for B→π0π0 and B→ρ0ρ0 decays.

Constrained φ2 using isospin analysis with the new data.

Abstract

We present a summary of measurements sensitive to the CKM angle $\phi_2$, performed by the Belle experiment using the final data sample of $772 \times 10^{6}$ $B\bar{B}$ pairs produced at the $\Upsilon(4S)$ resonance at the KEK asymmetric $e^+e^-$ collider. We discuss $CP$ asymmetries from the decay $B^{0} \rightarrow \pi^{+} \pi^{-}$ and briefly mention a preliminary measurement of the branching fraction of $B\to\pi^0\pi^0$ decays. Furthermore the measurement of the branching fraction of $B^{0}\rightarrow \rho^0\rho^0$ decays and fraction of longitudinal polarization in this decay is presented. We use the results to constrain $\phi_2$ with isospin analyses in the $B\rightarrow \pi\pi$ and $B\rightarrow\rho\rho$ systems.