Search for Gauge-Mediated SUSY Breaking Topologies at s∼\sqrt{s} \sim 189 GeV

Searches for topologies characteristic of Gauge Mediated SUSY Breaking models (GMSB) are performed by analysing 173.6 pb^-1 of data collected at Ecm = 188.6~GeV with the ALEPH detector.These topologies include acoplanar photons, non-pointing single photon, acoplanar leptons, large impact parameter leptons, detached slepton decay vertices, heavy stable charged sleptons and four leptons plus missing energy final states.No evidence for these new phenomena is observed and limits on production cross sections and sparticle masses are derived. A scan of a minimal GMSB parameter space is performed and model dependent lower limits of about 45 GeV/c^2 on the next-to-lightest supersymmetric particle (NLSP) mass and of about 9 TeV on the mass scale parameter Lambda are derived, independently of the NLSP lifetime

Measurement of the W Mass and Width in e+e−e^+ e^- Collisions at 189 GeV

The mass of the W boson is determined in e+e- collisions at LEP by the direct reconstruction of W decays in WW->qqqq and WW->lvqq events, supplemented by measurements using the kinematic properties of the leptons in the WW->lvlv decay channel. The main sample of W pairs is selected from an integrated luminosity of 174 pb^-1 collected with the ALEPH detector in 1998 at a centre-of-mass energy of 188.63 GeV.The combined result from all channels is mW = 80.432+-0.072(stat.)+-0.041(syst.)+-0.019(FSI)+-0.017(LEP) GeV/c^2, where FSI represents the possible effects of final state interactions in the qqqq channel. In a second two-parameter fit to the qqqq, evqq and mvqq channels, where the W mass and width are decoupled, the average W width is found to be 2.24+-0.20(stat.)+-0.13(syst.) GeV/c^2, consistent with the Standard Model prediction. The combination of the mass measurement presented in this paper together with those derived previously from the W pair cross section at 161 and 172 GeV and direct reconstruction at 172 and 183 GeV gives mW = 80.418+-0.061(stat.)+-0.038(syst.)+-0.019(FSI)+-0.017(LEP) Ge