Search for charginos and neutralinos in $e^+ e^-$ collisions at center-of-mass energies near 183-GeV and constraints on the MSSM parameter space

ALEPH Collaboration, The and Barate, R. and Betteridge, Andrew and Bowdery, Christopher and Colrain, Paul and Finch, Alexander and Foster, Frank and Hughes, Gareth and Jones, Roger and Williams, Mark (1999) Search for charginos and neutralinos in $e^+ e^-$ collisions at center-of-mass energies near 183-GeV and constraints on the MSSM parameter space. The European Physical Journal C (EPJ C) - Particles and Fields, 11 (2). pp. 193-216. ISSN 1434-6052

Abstract

Searches for charginos and neutralinos are performed with the data collected by the ALEPH detector at LEP at centre-of-mass energies near 183 GeV. 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 pb −1 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 GeV/ c2 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.