Evidence for the decay B0 →ηπ0

Abstract

We report a search for the charmless hadronic decay B0→ηπ0 with a data sample corresponding to an integrated luminosity of 694 fb-1 containing 753×106 BB¯ pairs. The data were collected by the Belle experiment running on the Y(4S) resonance at the KEKB e+e- collider. We measure a branching fraction B(B0→ηπ0)=(4.1-1.5-0.7+1.7+0.5)×10-7, where the first uncertainty is statistical and the second is systematic. Our measurement gives an upper limit of B(B0→ηπ0)<6.5×10-7 at 90% confidence level. The signal has a significance of 3.0 standard deviations and constitutes the first evidence for this decay mode.