Search for Chargino and Neutralino Production at sqrts = 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 cross-sections are obtained as a function of the chargino mass, the lightest neutralino mass and the second lightest neutralino mass. Within the Constrained Minimal Supersymmetric Standard Model framework, and for a chargino - neutralino mass difference of more than 5 GeV, the 95% confidence level lower limits on the chargino mass are 93.6 GeV for tanbeta = 1.5 and 94.1 GeV for tanbeta = 35. These limits are obtained assuming a universal scalar mass m0 > 500 GeV. The corresponding limits for all m0 are 78.0 and 71.7 GeV. The 95% confidence level lower limits on the lightest neutralino mass, valid for any value of tanbeta are 32.8 GeV for m0 > 500 GeV and 31.6 GeV for all m0.
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