Search for invisibly decaying Higgs bosons with large decay width using the OPAL detector at LEP

David Charlton, Predrag Jovanovic, Christopher Hawkes, Peter Watkins, Alan Watson, Nigel Watson, John Wilson

Research output: Contribution to journalArticle

4 Citations (Scopus)


This paper describes a topological search for an invisibly decaying Higgs boson, H, produced via the Bjorken process (e(+)e(-)-> HZ). The analysis is based on data recorded using the OPAL detector at LEP at centre-of-mass energies from 183 to 209 GeV corresponding to a total integrated luminosity of 629 pb(-1). In the analysis only hadronic decays of the Z boson are considered. A scan over Higgs boson masses from 1 to 120 GeV and decay widths from 1 to 3000 GeV revealed no indication for a signal in the data. From a likelihood ratio of expected signal and standard model background we determine upper limits on cross-section times branching ratio to an invisible final state. For moderate Higgs boson decay widths, these range from about 0.07 pb (M-H=60 GeV) to 0.57 pb (M-H=114 GeV). For decay widths above 200 GeV the upper limits are of the order of 0.15 pb. The results can be interpreted in general scenarios predicting a large invisible decay width of the Higgs boson. As an example we interpret the results in the so-called stealthy Higgs scenario. The limits from this analysis exclude a large part of the parameter range of this scenario experimentally accessible at LEP 2.
Original languageEnglish
Pages (from-to)457-472
Number of pages16
JournalEuropean Physical Journal C
Issue number2
Early online date6 Dec 2006
Publication statusPublished - 29 Jan 2007


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