Search for Neutral Higgs Bosons in e+e- Collisions at sqrt(s) ~189GeV

TL;DR

This paper reports a search for neutral Higgs bosons at LEP with the OPAL detector, setting mass limits and exclusion regions for both Standard Model and MSSM Higgs scenarios based on collision data at 189 GeV.

Contribution

First search to set experimental limits on neutral Higgs bosons at this energy, incorporating previous results and exploring MSSM parameter space.

Findings

Lower mass bound for SM Higgs: 91.0 GeV

MSSM Higgs mass limits: mh>74.8 GeV, mA>76.5 GeV

Excluded tan(beta) values between 0.72 and 2.19

Abstract

A search for neutral Higgs bosons has been performed with the OPAL detector at LEP, using approximately 170 pb-1 of e+e- collision data collected at sqrt(s)~189GeV. Searches have been performed for the Standard Model (SM) process e+e- to H0Z0 and the MSSM processes e+e- to H0Z0, A0h0. The searches are sensitive to the b b-bar and tau antitau decay modes of the Higgs bosons, and also to the MSSM decay mode h0 to A0A0. OPAL search results at lower centre-of-mass energies have been incorporated in the limits we set, which are valid at the 95% confidence level. For the SM Higgs boson, we obtain a lower mass bound of 91.0 GeV. In the MSSM, our limits are mh>74.8GeV and mA>76.5GeV, assuming tan(beta)>1, that the mixing of the scalar top quarks is either zero or maximal, and that the soft SUSY-breaking masses are 1 TeV. For the case of zero scalar top mixing, we exclude values of tan(beta) between 0.72 and 2.19.