KA / 2000 - 06 April 2000 Higgs Boson Searches at LEP Up To √ s = 202 GeV

The latest preliminary combined results of the Higgs boson searches from the LEP experiments ALEPH, DELPHI, L3 and OPAL are presented. A general scan of the MSSM parameters is performed and leads to stringent lower mass limits and for the first time excludes low tanβ values. Presented at the Seventh International Symposium on Particles, Strings, and Cosmology, PASCOS–99, Granlibakken, USA, Dec. 10–16, 1999 Higgs Boson Searches at LEP Up To √ s = 202 GeV André Sopczak Karlsruhe University E-mail: [email protected] The latest preliminary combined results of the Higgs boson searches from the LEP experiments ALEPH, DELPHI, L3 and OPAL are presented. A general scan of the MSSM parameters is performed and leads to stringent lower mass limits and for the first time excludes low tan β values. 1 Standard Model Higgs Boson The search for Higgs bosons at LEP shows no indication of a signal. This review includes the data from the outstanding performance of the LEP accelerator in 1999 with a collected luminosity of about 900 pb at √ s = 192 to 202 GeV . The confidence levels CLb for a signal observation and CLs for setting mass limits are shown in Fig. 1. The resulting Standard Model (SM) Higgs boson mass limit is 107.9 GeV/c at 95% CL. The reconstructed mass distribution is shown in Fig. 2. In extensions of the SM the HZZ coupling might be weaker and thus the production cross section is reduced. Figure 2 shows limits on the reduction factor at 95% CL. Even if the SM cross section is reduced by a factor three, a Higgs boson mass up to 103 GeV/c is excluded. 10 10 10 10 10 10 10 1 96 98 100 102 104 106 108 110 mH(GeV/c ) 1C L b LEP 189-202 Observed Expected signal Expected background 10 10 10 10 10 10 96 98 100 102 104 106 108 110 mH(GeV/c ) C L s 107.9 109.1 LEP 189-202