Searches for Invisible Higgs bosons: Preliminary combined results using LEP data collected at energies up to 209 GeV

In the year 2000 the four LEP experiments have collected data at energies between 200 and 209 GeV, for approximately 868 pb-1 integrated luminosity. The LEP working group for Higgs boson searches has combined these data with earlier data sets collected at lower centre-of-mass energies to search for a neutral CP-even Higgs boson, produced at the Standard Model rate, decaying into "invisible" particles. No statistically significant excess has been observed when compared to the Standard Model background prediction, and assuming that the Higgs boson decays only into such states a lower bound has been set on its mass at 95% confidence level of 114.4 GeV.