Search for $B\to h^{(*)}\nu \overline{\nu }$ Decays at Belle

We present a search for the rare decays $B\to h^{(*)}\nu \overline{\nu }$, where $h^{(*)}$ stands for a light meson. A data sample of $535\times {10}^6$ $B\overline{B}$ pairs collected with the Belle detector at the KEKB $e^{+}{e}^{-}$ collider is used. Signal candidates are required to have an accompanying $B$ meson fully reconstructed in a hadronic mode and signal side particles consistent with a single $h^{(*)}$ meson. No significant signal is observed and we set upper limits on the branching fractions at 90% confidence level. The limits on $B^0\to K^{*0}\nu \overline{\nu }$ and $B^{+}\to K^{+}\nu \overline{\nu }$ decays are more stringent than the previous constraints, while the first searches for $B^0\to K^0\nu \overline{\nu }$, ${\pi }^0\nu \overline{\nu }$, ${\rho }^0\nu \overline{\nu }$, $\varphi \nu \overline{\nu }$ and $B^{+}\to K^{*+}\nu \overline{\nu }$, ${\rho }^{+}\nu \overline{\nu }$ are reported.

Figure 1

The quark-level diagrams for $B\to K^{*}\nu \overline{\nu }$ decays.

Figure 2

The $E_{\mathrm{ECL}}$ distributions for $B\to h^{(*)}\nu \overline{\nu }$ decays. The shaded histograms show the background distributions from MC simulations and are normalized to sideband data. The open histograms show the SM expected signal distributions for $B\to K^{(*)}\nu \overline{\nu }$ decays multiplied by a factor of 20 for the comparison. The vertical dashed lines show the upper bound (left) of the signal box and the lower bound (right) of the sideband region.