Searches for Gauge-Mediated Supersymmetry Breaking Topologies in e+e- collisions at LEP2

TL;DR

This paper reports on searches for gauge-mediated supersymmetry breaking signatures in e+e- collisions at LEP2, setting limits on superpartner masses and model parameters due to the absence of observed signals.

Contribution

It provides the first comprehensive search across all NLSP lifetimes and constrains GMSB model parameters using LEP2 data.

Findings

No evidence for GMSB signatures was observed.

Excluded NLSP masses below specific thresholds at 95% CL.

Set lower bounds on the SUSY mass scale Lambda for various messenger indices.

Abstract

Searches were performed for topologies predicted by gauge-mediated Supersymmetry breaking models (GMSB). All possible lifetimes of the next-to-lightest SUSY particle (NLSP), either the lightest neutralino or slepton, decaying into the lightest SUSY particle, the gravitino, were considered. No evidence for GMSB signatures was found in the OPAL data sample collected at centre-of-mass energies of sqrt{s}=189-209 GeV at LEP. Limits on the product of the production cross-sections and branching fractions are presented for all search topologies. To test the impact of the searches, a complete scan over the parameters of the minimal model of GMSB was performed. NLSP masses below 53.5 GeV/c^2 in the neutralino NLSP scenario, below 87.4 GeV/c^2 in the stau NLSP scenario and below 91.9 GeV/c^2 in the slepton co-NLSP scenario are excluded at 95% confidence level for all NLSP lifetimes. The scan determines constraints on the universal SUSY mass scale Lambda from the direct SUSY particle searches of Lambda > 40,27,21,17,15 TeV/c^2 for messenger indices N=1,2,3,4,5 for all NLSP lifetimes.