Steven Robertson
SLAC

 A search for  B- to K- nu nubar

We present a search for the rare flavour-changing neutral-current decay
B- to K- nu  nubar a sample of (86.9 +/- 1.0) X 10^6  Upsilon(4S) to
B Bbar events collected by the BaBar experiment
at the SLAC B-factory.  Signal candidate events are selected by fully
reconstructing a B+ to D0 X+ decay, where X+ represents a combination of up
to three charged pions or kaons and up to two pi0 candidates.  The
charged tracks and calorimeter clusters not used in the B+ reconstruction are 
required to be compatible with a B- to K- nu nubar decay. We observe a total 
of three signal candidate events with an expected background of 2.7 +/-0.8, 
resulting in a preliminary limit of B(B- to K- nu  nubar) < 1.05 X 10^{-4}
at the 90% confidence level.  This search is combined with the results of a 
previous and statistically independent preliminary BaBar search for
B- to K- nu  nubar to give a limit of  B(B- to K- nu nubar) < 7.0 X 10^{-5}
at the 90% confidence level.