A search for the decay $B^+ \to K^+ \nu \bar{\nu}$

TL;DR

This study searches for the rare decay $B^+ o K^+ u ar{ u}$ using data from the BABAR detector, setting upper limits on its branching fraction and exploring related decay modes.

Contribution

First search for $B^+ o K^+ u ar{ u}$ decay using hadronic and semileptonic B reconstruction methods, establishing new upper limits on its branching fraction.

Findings

Branching fraction limit for $B^+ o K^+ u ar{ u}$: < 5.2 x 10^{-5}

Branching fraction limit for $B^+ o  u ar{ u}$: < 1.0 x 10^{-4}

Used 82 fb$^{-1}$ data sample from BABAR detector

Abstract

We search for the rare flavor-changing neutral-current decay $B^+ \to K^+ \nu \bar{\nu}$ in a data sample of 82 fb$^{-1}$ collected with the {\sl BABAR} detector at the PEP-II B-factory. Signal events are selected by examining the properties of the system recoiling against either a reconstructed hadronic or semileptonic charged-B decay. Using these two independent samples we obtain a combined limit of ${\mathcal B}(B^+ \to K^+ \nu \bar{\nu})<5.2 \times 10^{-5}$ at the 90% confidence level. In addition, by selecting for pions rather than kaons, we obtain a limit of ${\mathcal B}(B^+ \to \pi^+ \nu \bar{\nu})<1.0 \times 10^{-4}$ using only the hadronic B reconstruction method.