2022 Impact factor 4.4
Particles and Fields
Eur. Phys. J. C 12, 567-586
DOI 10.1007/s100520000286

Search for neutral Higgs bosons in e+ e- collisions at $\sqrt s \approx$ 189GeV

The OPAL Collaboration

G.Abbiendi 2 - et al.

Dipartimento di Fisica dell' Università di Bologna and INFN, 40126 Bologna, Italy

Received: 9 July 1999 / Published online: 27 January 2000 - © Springer-Verlag 2000 2000

Searches for the neutral Higgs bosons predicted by the Standard Model (SM) and the Minimal Supersymmetric extension of the Standard Model (MSSM) have been performed with the OPAL detector at LEP. Approximately 170pb-1 of e+ e- collision data collected at $\sqrt{s}
\approx 189$GeV were used to search for Higgs boson production in the SM process ${\mathrm{e}}^+ {\mathrm{e}}^- \rightarrow \mathrm{H}^{0}
\mathrm{Z}^{0}$ and the MSSM processes ${\mathrm{e}}^+ {\mathrm{e}}^-
\rightarrow \mathrm{h}^{0} \mathrm{Z}^{0}$ and ${\mathrm{e}}^+
{\mathrm{e}}^- \rightarrow \mathrm{A}^{0} \mathrm{h}^{0}$. The searches are sensitive to the $\mathrm{b}\bar{\mathrm{b}}$ and $\tau^+\tau^-$decay modes of the Higgs bosons, and also to the MSSM decay mode $\mathrm{h}^{0} \rightarrow \mathrm{A}^{0} \mathrm{A}^{0}$. OPAL search results at lower centre-of-mass energies have been incorporated in the limits, which are valid at the 95% confidence level. For the SM Higgs boson, a lower mass bound of 91.0GeV is obtained. In the MSSM, the 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 1TeV. For the case of zero scalar top mixing, the values of $\tan\beta$ between 0.72 and 2.19 are excluded.

Copyright Springer-Verlag 2000