A search for a Higgs boson decaying into invisible particles is performed u
sing the data collected at LEP by the L3 experiment at centre-of-mass energ
ies of 183 GeV and 189 GeV. The integrated luminosities are respectively 55
.3 pb(-1) and 176.4 pb(-1). The observed candidates are consistent with the
expectations from Standard Model processes. In the hypothesis that the pro
duction cross section of this Higgs boson equals the Standard Model one and
the branching ratio into invisible particles is 100%, a lower mass limit o
f 89.2 GeV is set at 95% confidence level. (C) 2000 Elsevier Science B.V. A
ll rights reserved.