Search for $B\to K^{*}\nu \overline{\nu }$ decays

We present a search for the decays $B\to K^{*}\nu \overline{\nu }$ using $454\times {10}^{6}B\overline{B}$ pairs collected at the ${\rm Y}(4S)$ resonance with the BABAR detector at the SLAC PEP-II $B$-Factory. We first select an event sample where one $B$ is reconstructed in a semileptonic or hadronic mode with one charmed meson. The remaining particles in the event are then examined to search for a $B\to K^{*}\nu \overline{\nu }$ decay. The charged $K^{*}$ is reconstructed as $K^{*+}\to K_S^0{\pi }^{+}$ or $K^{*+}\to K^{+}{\pi }^0$; the neutral $K^{*}$ is identified in $K^{*0}\to K^{+}{\pi }^{-}$ mode. We establish upper limits at 90% confidence level of $\mathcal{B}(B^{+}\to K^{*+}\nu \overline{\nu })<8\times {10}^{-5}$, $\mathcal{B}(B^0\to K^{*0}\nu \overline{\nu })<12\times {10}^{-5}$, and $\mathcal{B}(B\to K^{*}\nu \overline{\nu })<8\times {10}^{-5}$.

Figure 1

SM diagrams for $b\to s\nu \overline{\nu }$ transitions.

Figure 2

The $D$ mass (a) and the CM momentum of the $B_{\mathrm{sl}}$ lepton (b), in the SL analysis from MC simulations (histogram, the hatched area shows the continuum contribution), on-peak data (solid circle) and luminosity scaled off-peak data (open circle). Events where in the signal side a $K^{*+}\to K^{+}{\pi }^0$ channel is reconstructed are shown.

Figure 3

The $m_{\mathrm{ES}}$ distributions for charged (a) and neutral (b) $B_{\mathrm{had}}$. The points represent the on-peak data and the hatched area shows the estimated background contribution.

Figure 4

Fit results: (a)–(c) for the extra EMC energy $E_{\mathrm{extra}}$ in the SL analysis; (d)–(f) for the neural network output $N{N}_{\mathrm{out}}$ in the HAD analysis. From left to right, $K^{*+}\to K^{+}{\pi }^0$, $K^{*+}\to K_S^0{\pi }^{+}$, and $K^{*0}\to K^{+}{\pi }^{-}$. Data are shown as points, and the fit result is shown with a solid line. The dotted and dashed lines show the estimated signal and background contributions, respectively.