We report the first observation of a near-threshold enhancement in the $D^0\bar{ D}^0\pi^0$ system from $B \to D^0\bar{ D}^0\pi^0 K$ decays using a 414 $\mathrm{ fb}^{ -1}$ data sample collected at the $\Upsilon(4S)$ resonance. The enhancement peaks at a mass $M=3875.4 \pm 0.7_{ -2.0}^{ +1.2}$ MeV/$c^2$ and the branching fraction for events in the peak is \Br ($B \to D^0\bar{ D}^0\pi^0 K$)=(1.27 $\pm$ 0.31 $_{ -0.39}^{ +0.22})$ $\times$ $10^{ -4}$. The data were collected with the Belle detector at the KEKB energy-asymmetric $e^+e^-$ collider.
Categories: hep-ex