A total of 628 bp-1 of data collected with the ALEPH detector at centre-of-mass energies from 189 to 209 GeV is analysed in the search for gauge mediated SUSY breaking (GMSB) topologies. These ...topologies include two acoplanar photons, non-pointing single photons, acoplanar leptons, large impact parameter leptons, detached slepton decay vertices, heavy stable charged sleptons and multi-leptons plus missing energy final states. No evidence is found for new phenomena, and lower limits on masses of supersymmetric particles are derived. A scan of a minimal GMSB parameter space is performed and lower limits are set for the next-to-lightest supersymmetric particle (NLSP) mass at 54 GeV/c2 and for the mass scale parameter \(\Lambda\) at 10 TeV/c2, independently of the NLSP lifetime. Including the results from the neutral Higgs boson searches, a NLSP mass limit of 77 GeV/c2 is obtained and values of \(\Lambda\) up to 16 TeV/c2 are excluded.
Two-particle correlations in pp, p¯p¯ and KS0KS0 pairs have been studied in hadronic Z decays recorded at LEP with the ALEPH detector. The correlations were measured as a function of the ...four-momentum difference Q of the pair. For pp, p¯p¯ pairs a depletion of events is observed in the region Q<3 GeV, and for KS0KS0 pairs an enhancement of events is observed in the region Q<0.5 GeV. These features are consistent with expectations from Fermi–Dirac and Bose–Einstein statistics, respectively.
In its second phase, LEP has allowed to study four fermion processes never
observed before. Results are presented on the charged triple gauge boson
couplings (TGC) from the W-pair, Single W and ...Single gamma production. The
anomalous quartic gauge couplings (QGC) are constrained using production of
WWgamma, nunubargammagamma and Zgammagamma final states. Finally, limits on the
neutral anomalous gauge couplings (NGC) using the Zgamma and ZZ production
processes are also reported. All results are consistent with the Standard Model
expectations.
The rate of gluon splitting into cc̄ pairs in hadronic Z decays is measured using the data sample collected by ALEPH from 1991 to 1995. The selection is based on the identification of leptons ...(electrons and muons) originating from semileptonic charm decays, and on the topological properties of signal events. The result derived from the selected sample is gcc̄=(3.26±0.23(stat)±0.42(syst))%.
Events containing only energetic photons are analysed in a sample of 628 pb -1 of data recorded from e+e- collisions at centre-of-mass energies between 189 and 209 GeV by the ALEPH detector at LEP. ...The $\reenunug$ and $\reeggg$ cross sections are measured and found to be in agreement with the Standard Model predictions. The number of light neutrino generations is determined to be N_\nu = 2.86 \pm 0.09. Upper limits are derived on the cross sections for photon production in the context of several supersymmetric models. Limits are also set on the parameters of models with extra spatial dimensions with contact interactions and with excited electrons.
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