LIMITS ON ASSOCIATED PRODUCTION OF VISIBLY AND INVISIBLY DECAYING HIGGS-BOSONS FROM Z-DECAYS

Many extensions of the standard electroweak model Higgs sector suggest that the main Higgs decay channel is ''invisible'', for example, h -- > JJ where J denotes the majoron, a weakly interacting pseudoscalar Go ldstone boson associated to the spontaneous violation of lepton number . In many of these models the Higgs boson may also be produced in asso ciation to a massive pseudoscalar boson (HA), in addition to the stand ard Bjorken mechanism (HZ). We describe a general strategy to determin e limits from LEP data on the masses and couplings of such Higgs boson s, using the existing data on acoplanar dijet events as well as data o n four and six b jet event topologies. For the sake of illustration, w e present constraints that can be obtained for the ALEPH data.