Search for Supersymmetric Particles in e+e- Collisions at sqrt(s) up to 202GeV and Mass Limit for the Lightest Neutralino

TL;DR

This paper reports on searches for supersymmetric particles at LEP energies up to 202 GeV, setting new mass limits for the lightest neutralino and constraining MSSM and supergravity models based on null results.

Contribution

It provides the first comprehensive search results at these energies, establishing new exclusion limits for supersymmetric particles and refining MSSM parameter space constraints.

Findings

No evidence of supersymmetric particles was observed.

A 95% confidence level lower limit of 37 GeV/c^2 was set on the lightest neutralino mass.

Constraints on MSSM and supergravity models were improved.

Abstract

Searches for pair production of squarks, sleptons, charginos, and neutralinos are performed with the data collected by the ALEPH detector at LEP at centre-of-mass energies from 188.6 to 201.6 GeV. No evidence for any such signals is observed in a total integrated luminosity of about 410pb-1. The negative results of the searches are translated into exclusion domains in the space of the relevant MSSM parameters, which improve significantly on the constraints set previously. Under the assumptions of gaugino and sfermion mass unification, these results allow a 95% C.L. lower limit of 37GeV/c2 to be set on the mass of the lightest neutralino for any tan beta and sfermion mass. Additional constraints in the MSSM parameter space are derived from the negative results of ALEPH searches for Higgs bosons. The results are also interpreted in the framework of minimal supergravity.