Evidence for the decay B0->eta pi^0

Abstract

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

11 pages, 3 figures, 2 tables, submitted to Physical Review D(R)