Search for charginos and neutralinos
in e+e- collisions
at centre-of-mass energies near 183GeV
constraints on the MSSM parameter space
The ALEPH Collaboration
R. Barate - et al.
Laboratoire de Physique des Particules (LAPP), IN2P3-CNRS,
F-74019 Annecy-le-Vieux Cedex, France
Received: 8 February 1999 / Published online: 8 September 1999
Searches for charginos and neutralinos are performed with the data collected by the ALEPH detector at LEP at centre-of-mass energies near 183GeV. In these searches, it is assumed that R-parity is conserved and that the lightest neutralino is the LSP. No evidence of a signal is observed in the 57 accumulated, which excludes chargino and associated neutralino production up to the kinematic limit over large regions of the MSSM parameter space. Under the assumptions of common gaugino and common sfermion masses at the unification scale, the interplay between the chargino, neutralino and slepton exclusion limits allows a lower bound of 27 to be set on the mass of the lightest neutralino. Tighter constraints on the MSSM parameter space are obtained using in addition exclusions in the Higgs sector. Finally, the results are interpreted within the framework of minimal supergravity.