Study of $B^{+}\to p\bar{n}{\pi }^0$

We search for the tree-diagram dominated process $B^{+}\to p\bar{n}{\pi }^0$, using a data sample of $772\times {10}^{6}B\bar{B}$ pairs collected at the $\mathrm{{\rm Y}}(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. This is the first search with the Belle detector for a decay mode including an anti-neutron. No significant signal is observed and an $90\mathrm{\%}$ credible upper limit on the branching fraction is set at $6.1\times {10}^{-6}$.