Improved measurement of $B^0 \to \pi^0 \pi^0$

TL;DR

This paper presents an improved measurement of the branching fraction and CP asymmetry for the decay $B^0 o c0c0$ using a large data sample from the Belle experiment, achieving significant results.

Contribution

The study provides the most precise measurement to date of the branching fraction and CP asymmetry for $B^0 o c0c0$ decay, enhancing understanding of CP violation.

Findings

Branching fraction measured as 1.1 1.3 imes 10^{-6}.

CP asymmetry reported as 0.44 with large uncertainties.

Significance of the decay observation is 5.4 sigma.

Abstract

We report an improved measurement of the decay $B^0 \to \pi^0 \pi^0$, using a data sample of 535 $\times 10^6 B\bar{B}$ pairs collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric energy $e^+ e^-$ collider. The measured branching fraction is ${\cal B}(B^0 \to \pi^0 \pi^0) = 1.1\pm 0.3(stat.) \pm 0.1(syst.)$, with a significance of 5.4 standard deviations including systematic uncertainties. We also report the partial rate asymmetry: $\acp(B^0 \to \pi^0 \pi^0)$ = 0.44 $^{+0.73}_{-0.62}$(stat.)$^{+0.04}_{-0.06}$(syst.).