Evidence for the decay B0->eta pi^0

TL;DR

This paper reports the first evidence for the rare decay B0->eta pi^0, measuring its branching fraction and setting an upper limit, based on a large data sample from the Belle experiment at KEKB.

Contribution

It provides the first experimental evidence for the decay B0->eta pi^0 and measures its branching fraction using data from the Belle detector.

Findings

Branching fraction of (4.1^{+1.7+0.5}_{-1.5-0.7})×10^{-7}

Evidence with 3.0 sigma significance

Upper limit of 6.5×10^{-7} at 90% CL

Abstract

We report a search for the charmless hadronic decay $B^0\to\eta \pi^0$ with a data sample corresponding to an integrated luminosity of 694 $\rm fb^{-1}$ containing $753\times10^6$ $B\bar{B}$ pairs. The data were collected by the Belle experiment running on the $\Upsilon(4S)$ resonance at the KEKB $e^+e^-$ collider. We measure a branching fraction $\mathcal{B}(B^0\to\eta\pi^0)=(4.1^{+1.7+0.5}_{-1.5-0.7})\times 10^{-7}$, where the first uncertainty is statistical and the second is systematic. Our measurement gives an upper limit of $\mathcal{B}(B^0\to\eta\pi^0)<6.5\times 10^{-7}$ at 90\% confidence level. The signal has a significance of $3.0$ standard deviations and constitutes the first evidence for this decay mode.