Mass Limits of Invisibly Decaying Higgs Particles from the LEP Data

In the Majoron models the $SU(2)$ doublet Higgs can decay invisibly into a Majoron pair via its mixing with a singlet. An analysis of the LEP data shows the invisible decay mode to be more visible than the SM decay. For these models, the dominantly doublet Higgs $H$ is shown to have a mass limit within $\pm 6$ GeV of the SM limit irrespective of the model parameters. But the dominantly singlet one $S$ can be arbitrarily light for sufficiently small mixing angle.