Search for supersymmetric particles in scenarios with a gravitino LSP and stau NLSP

Sleptons, neutralinos and charginos were searched for in the context of scenarios where the lightest supersymmetric particle is the gravitino. It was assumed that the stau is the next-to-lightest supersymmetric particle. Data collected with the DELPHI detector at a centre-of-mass energy near 189 GeV were analysed combining the methods developed in previous searches at lower energies. No evidence for the production of these supersymmetric particles was found. Hence, limits were derived at 95% confidence level.Comment: 31 pages, 14 figure

Search for lightest neutralino and stau pair production in light gravitino scenarios with stau NLSP

Promptly decaying lightest neutralinos and long-lived staus are searched for in the context of light gravitino scenarios. It is assumed that the stau is the next to lightest supersymmetric particle (NLSP) and that the lightest neutralino is the next to NLSP (NNLSP). Data collected with the Delphi detector at centre-of-mass energies from 161 to 183 GeV are analysed. No evidence of the production of these particles is found. Hence, lower mass limits for both kinds of particles are set at 95% C.L.. The mass of gaugino-like neutralinos is found to be greater than 71.5 GeV/c(2). In the search for long-lived stau: masses less than 70.0 to 77.5 GeV/c(2) are excluded for gravitino masses from 10 to 150 eV/c(2). Combining this search with the searches for stable heavy leptons and minimal supersymmetric standard model staus a lower limit of 68.5 GeV/c(2) may be set for the stau mass independent of the mass of the gravitino

Search for sleptons in e(+)e(-) collisions at root s=183 to 189 GeV

Data taken by the DELPHI experiment at centre-of-mass energies of 183 GeV and 189 GeV with a total integrated luminosity of 212 pb(-1) have been used to search for the supersymmetric partners of the electrons, muons, and taus in the context of the Minimal Supersymmetric Standard Model (MSSM). The decay topologies searched for were the direct decay ((l) over tilde --> l<(<chi>)over tilde>(0)(1)); producing acoplanar lepton pairs plus missing energy, and the cascade decay ((l) over tilde --> l<(<chi>)over tilde>(0)(2) -->l gamma<(<chi>)over tilde>(0)(1)), producing acoplanar lepton and photon pairs plus missing energy. The observed number of events is in agreement with Standard Model predictions. The 95% CL excluded mass limits for selectrons, smuons and staus are m((e) over bar) less than or equal to 87 GeV/c(2), m(<(<mu>)over bar>) less than or equal to 80 GeV/c(2) and m(<(<tau>)over bar>) less than or equal to 75 GeV/c(2), respectively, for values of mu = -200 GeV/c(2) and tan beta = 1.5. RI Ragazzi, Stefano/D-2463-2009; Gonzalez Caballero, Isidro/E-7354-2010; Krammer, Manfred/A-6508-2010; Katsanevas, Stavros/A-4297-2011; Ruiz, Alberto/E-4473-2011; Andreazza, Attilio/E-5642-2011; Marti-Garcia, Salvador/F-3085-2011; Verzi, Valerio/B-1149-2012; Shellard, Ronald/G-4825-2012; Petrolini, Alessandro/H-3782-2011; Fruhwirth, Rudolf/H-2529-2012; Monge, Maria Roberta/G-9127-201