Abstract
A search for the Higgsstrahlung process e+e−→hZ is described, where the neutral Higgs boson h is assumed to decay into hadronic final states. In order to be sensitive to a broad range of models, the search is performed independent of the flavour content of the Higgs boson decay. The analysis is based on e+e− collision data collected by the OPAL detector at energies between 192 and 209 GeV. The search does not reveal any significant excess over the Standard Model background prediction. Results are combined with previous searches at energies around 91 and at 189 GeV. A limit is set on the product of the cross-section and the hadronic branching ratio of the Higgs boson, as a function of the Higgs boson mass. Assuming the hZ coupling predicted by the Standard Model, and a Higgs boson decaying only into hadronic final states, a lower bound of 104 GeV/c2 is set on the mass at the 95% confidence level.
Highlights
In the Standard Model (SM) and for masses relevant to the LEP energy range, the Higgs boson is predicted to be produced principally by the Higgsstrahlung process e+e− → hZ and to decay dominantly into the bbchannel
604 candidates are selected, while 588 ± 56 are expected from background processes
The four analyses are split into several sub-channels denoted by i depending on the value of the discriminating variable
Summary
In the Standard Model (SM) and for masses relevant to the LEP energy range, the Higgs boson is predicted to be produced principally by the Higgsstrahlung process e+e− → hZ and to decay dominantly into the bbchannel. In order to be sensitive to Higgs bosons predicted by such models, the search described here is based only on kinematic selections which are insensitive to the hadron flavour present in the final state. A variety of Monte Carlo samples have been generated to estimate the selection efficiencies for the Higgs the range of energies boson of the signal data, and the for the background processes. For each of the search channels, the effect of the preselection and likelihood cuts on the data samples, the total background and its contributions, and on the signal detection efficiency for two test-masses can be followed through Table 1.
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