Search for Charginos and Neutralinos in e+e- collisions at \sqrt{s} = 189 Gev

TL;DR

This study searched for charginos and neutralinos in electron-positron collisions at 189 GeV, setting new limits on their production and masses within the Minimal Supersymmetric Standard Model, with no evidence of their existence found.

Contribution

First to set experimental limits on charginos and neutralinos at 189 GeV, improving constraints on their masses and parameter space in the MSSM.

Findings

No evidence for charginos or neutralinos was observed.

Established lower mass limits: 32.5 GeV for the lightest neutralino, 67.7 GeV for the lightest chargino.

Derived new exclusion regions in the MSSM parameter space.

Abstract

We report the result of a search for charginos and neutralinos, in e+e- collisions at 189 GeV centre-of-mass energy at LEP. No evidence for such particles is found in a data sample of 176 pb^{-1}. Improved upper limits for these particles are set on the production cross sections. New exclusion contours in the parameter space of the Minimal Supersymmetric Standard Model are derived, as well as new lower limits on the masses of these supersymmetric particles. Under the assumptions of common gaugino and scalar masses at the GUT scale, we set an absolute lower limit on the mass of the lightest neutralino of 32.5 GeV and on the mass of the lightest chargino of 67.7 GeV.