Search for invisibly decaying Higgs bosons in e+e- -> Zoho production at sqrt(s) = 183 - 209 GeV

摘要

A search is performed for Higgs bosons decaying into invisible final states,produced in association with a Zo boson in e+e- collisions at energies between183 and 209 GeV. The search is based on data samples collected by the OPALdetector at LEP corresponding to an integrated luminosity of about 660 pb-1.The analysis aims to select events containing the hadronic decay products ofthe Zo boson and large missing momentum, as expected from Higgs boson decayinto a pair of stable weakly interacting neutral particles, such as thelightest neutralino in the Minimal Supersymmetric Standard Model. The sameanalysis is applied to a search for nearly invisible Higgs boson cascade decaysinto stable weakly interacting neutral particles. No excess over the expectedbackground from Standard Model processes is observed. Limits on the productionof invisibly decaying Higgs bosons produced in association with a Zo boson arederived. Assuming a branching ratio BR(ho->invisible)=1, a lower limit of 108.2GeV is placed on the Higgs boson mass at the 95% confidence level. Limits onthe production of nearly invisibly decaying Higgs bosons are also obtained.