Evidence for the decay B0->eta pi^0

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.