Search for neutral Higgs bosons in e$^+$e$^-$ collisions at $\sqrt{s}=183$ GeV

Neutral Higgs bosonswere searched for in the data collected by DELPHI at a centre-of-mass energy of 183 GeV, corresponding to an integrated luminosity of 54 pb\(^{-1}\). The production of the lightest neutral Higgs bosonwith either an on-shell Z bosonor a neutral pseudo-scalar Higgs bosonwas analysed. Lower limits at the 95% confidence level were obtained on the Higgs bosonmasses. The limits are 85.7 GeV/\(c^2\) for the Standard Model Higgs bosonand 74.4 GeV/\(c^2\) for the scalar and 75.3 GeV/\(c^2\) for the pseudo-scalar Higgs bosonsas predicted by the minimal super-symmetric extension of the Standard Modelwith commonly used assumptions on the model parameters, plus the assumption that the mass of the pseudo- scalar bosonis greater than 20 GeV/\(c^2\). These results significantly improve the limits reached with previous data.