Search for neutral Higgs bosons in the minimal supersymmetric extension of the standard model

Abstract

A search for the neutral Higgs bosons h⁰ and A⁰, predicted by the Minimal Supersymmetric Extension of the Standard Model (MSSM), has been performed by the OPAL Collaboration at LEP. The analysis was based on approximately 75 pb⁻¹ of data taken at centre-of-mass energies in the vicinity of the Z⁰ resonance. No Higgs boson signals have been detected. Using, in addition, an upper limit on the contribution of non-Standard Model processes to the Z⁰ boson width, almost the entire MSSM parameter space that can be reached at present LEP energies has been excluded. In particular, at the 95% confidence level, our results imply that$m_{h^0 } > 44.5$ GeV/c² and$m_{A^0 } > 24.3$ GeV/c², for tan β≥1. The sensitivity to this assumption is discussed and the search results are also interpreted in the context of general two-doublet models.