Search for chargino and neutralino production at √s = 189 GeV at LEP

Abstract

A search for charginos and neutralinos, predicted by supersymmetric theories, is performed using a data sample of 182.1 pb-1 taken at a centre-of-mass energy of 189 GeV with the OPAL detector at LEP. No evidence for chargino or neutralino production is found. Upper limits on chargino and neutralino pair production (X̃1+X̃1-, X̃10X̃20) cross-sections are obtained as a function of the chargino mass (mX̃1±), the lightest neutralino mass (mX̃10) and the second lightest neutralino mass (mX̃20). Within the Constrained Minimal Supersymmetric Standard Model framework, and for mX̃1± - mX̃10 ≥ 5 GeV, the 95% confidence level lower limits on mX̃1± are 93.6 GeV for tan β = 1.5 and 94.1 GeV for tan β = 3..