A search for the production and non-standard decay of a Higgs boson, h, into four taus through intermediate pseudoscalars, a, is conducted on 683 pb−1 of data collected by the ALEPH experiment at centre-of-mass energies from 183 to 209 GeV. No excess of events above background is observed, and exclusion limits are placed on the combined production cross section times branching ratio, \( {\xi^2} = \frac{{\sigma \left( {{\text{e}^{+} }{\text{e}^{-} } \to {\text{Zh}}} \right)}}{{{\sigma_{\text{SM}}}\left( {{\text{e}^{+} }{\text{e}^{-} } \to {\text{Zh}}} \right)}} \times B\left( {h \to {\text{aa}}} \right) \times B{\left( {{\text{a}} \to {\tau^{+} }{\tau^{-} }} \right)^2} \). For m h < 107 GeV/c 2 and 4 < m a < 10 GeV/c 2, ξ 2 > 1 is excluded at the 95% confidence level.

The ZZ production cross section is measured from a data sample corresponding to a total integrated luminosity of 452 pb−1, collected by the ALEPH experiment at LEP at centre-of-mass energies from 192 to 209 GeV. Individual cross sections, extracted at six centre-of-mass energies, are found to be in agreement with Standard Model calculations. The results are used to set limits on anomalous neutral gauge couplings.

Cross sections, angular distributions and forward-backward asymmetries are presented, of two-fermion events produced in e+e- collisions at centre-of-mass energies from 189 to 209 GeV at LEP, measured with the ALEPH detector. Results for e+e-, mu+mu-, tau+tau-, qq, bb and cc production are in agreement with the Standard Model predictions. Constraints are set on scenarios of new physics such as four-fermion contact interactions, leptoquarks, Z' bosons, TeV-scale quantum gravity and R-parity violating squarks and sneutrinos.

Inclusive beauty-quark production in two-photon collisions has been measured at LEP using an integrated luminosity of 698 pb-1 collected by the ALEPH detector with sqrt(s) between 130 and 209 GeV. The b quarks were identified using lifetime information. The cross section is found to be sigma(e+ e- --> e+ e- b \bar{b} X) = (5.4 +/- 0.8 (stat) +/- 0.8 (syst)) pb which is consistent with Next-to-Leading Order QCD.

A search for Higgs bosons produced in association with a fermion pair, and decaying to WW, is performed with the data collected by the ALEPH detector at centre-of-mass energies ranging from 191 to 209 GeV. The data correspond to an integrated luminosity of 453.2 pb-1. Thirteen exclusive selections are developed according to the different final state topologies. No statistically significant evidence for a Higgs boson decaying into a WW pair has been found. An upper limit is derived, as a function of the Higgs boson mass, on the product of the e+e-→Hff̄ cross section and the H→WW branching ratio. The data on the search for H→WW are combined with previously published ALEPH results on the search for H→γγ, to significantly extend the limits on the mass of a fermiophobic Higgs boson.

Deuteron and anti-deuteron production in Z decays has been observed in the ALEPH experiment at LER The production rate of anti-deuterons is measured to be (5.9 +/- 1.8 +/- 0.5) x 10(-6) per hadronic Z decay in the anti-deuteron momentum range from 0.62 to 1.03 GeV/c. The coalescence parameter B-2, which characterizes the likelihood of anti-deuteron production, is measured to be 0.0033 +/- 0.0013 GeV2 in Z decays. These measurements indicate that the production of anti-deuterons is suppressed in e(+)e(-) collisions compared to that in pp and photoproduction collisions. (c) 2006 Elsevier B.V. All rights reserved.

A review of the present status of the W boson mass and width measurements at LEP is presented. The analysis of the data collected in 1998 by the 4 LEP collaborations, corresponding to about 700 pb(-1), allows to reach an experimental uncertainty on the W boson mass measured at LEPII approaching the precision of the indirect results from the high precision electroweak measurements at LEPI.

Hadronic Z decays into three jets are used to test QCD models of colour reconnection (CR). A sensitive quantity is the rate of gluon jets with a gap in the particle rapidity distribution and zero jet charge. Gluon jets are identified by either energy-ordering or by tagging two b-jets. The rates predicted by two string-based tunable CR models, one implemented in JETSET (the GAL model), the other in ARIADNE, are too high and disfavoured by the data, whereas the rates from the corresponding non-CR standard versions of these generators are too low. The data can be described by the GAL model assuming a small value for the R0 parameter in the range 0.01-0.02.

Two-particle correlations in pp, (p) over bar(p) over bar and K-S(0) K-S(0) 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) over bar(p) over bar pairs a depletion of events is observed in the region Q < 3 GeV, and for (KSKS0)-K-0 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. (c) 2004 Elsevier B.V. All rights reserved.

Triple gauge-boson couplings gamma WW and ZWW involving single-photon, single-W and W-pair production are determined using data samples collected at LEP with the ALEPH detector at centre-of-mass energies between 183 and 209 GeV The integrated luminosity used is 700 pb(-1) for the single-photon measurement and 683 pb-1 for the W channels. Restricting the measurement to C- and P-conserving terms and applying local SU(2)(L) x U(1)(Y) gauge invariance, the measured values of the parameters g(1)(Z), kappa(gamma) and lambda(gamma) are:g(1)(Z) = 1.001 +/- 0.027(stat) +/- 0.013(syst),kappa(gamma) = 0.971 +/- 0.055(stat) +/- 0.030(syst),lambda(gamma) = -0.012 +/- 0.027(stat) +/- 0.011(syst)for single-parameter fits, where the two other parameters are fixed to their Standard Model values. Results are also presented for the cases where two or all three couplings are allowed to vary. An additional analysis using W-pair events is performed to measure the unconstrained real and imaginary parts of all 14 triple gauge-boson couplings and to perform an indirect search for a techni-p resonance. No deviations from the Standard Model expectations are observed and the lower limit on the techni-p mass is set to 600 GeV/c(2) at 95% confidence level. (c) 2005 Elsevier B.V. All rights reserved.

Bose-Einstein correlations in W-pair decays are studied using data collected by the ALEPH detector at LEP at e(+)e(-) centre-of-mass energies from 183 to 209 GeV. The analysis is based on the comparison of WW --> q (q) over barq (q) over bar events to "mixed" events constructed with the hadronic part of WW --> q (q) over bar lv events. The data are in agreement with the hypothesis that Bose-Einstein correlations are present only for pions from the same W decay. The JETSET model with Bose-Einstein correlations between pions from different W bosons is disfavoured. (C) 2004 Elsevier B.V. All rights reserved.

The cross sections for single vector boson production in the Wenu and Zee channels are measured from the data collected by AA the ALEPH detector at LEP for centre-of-mass energies between 183 and 209 GeV. These data correspond to a total integrated luminosity of 683 pb(-1). Single-W production is studied in both hadronic and leptonic decay channels. Hadronic and dimuon decays are used for single-Z production. The measured cross sections agree with the Standard Model predictions. (C) 2004 Elsevier B.V. All rights reserved.

The acoplanar photon pairs produced in the reaction e+e−→νν¯γγ are analysed in the 700 pb−1 of data collected by the ALEPH detector at centre-of-mass energies between 183 and 209 GeV. No deviation from the Standard Model predictions is seen in any of the distributions examined. The resulting 95% C.L. limits set on the anomalous QGCs, a0Z, acZ, a0W and acW, are −0.012

Charginos and neutralinos are searched for in the data collected by the ALEPH experiment at LEP for centre-of-mass energies up to 209 GeV. The negative result of these searches is combined with those from searches for sleptons and Higgs bosons to derive an absolute lower limit of 43.1 GeV/c(2) on the mass of the lightest supersymmetric particle (LSP), assumed to be the,lightest neutralino. This limit is obtained in the framework of the MSSM with R-parity conservation and with gaugino and sfermion mass unification at the GUT scale and assuming no mixing in the stau sector. The LSP limit degrades only slightly to 42.4 GeV/c(2) if stau mixing is considered. Within the more constrained framework of minimal supergravity, the limit is 50 GeV/c(2). (C) 2004 Published by Elsevier B.V.

Exclusive production of π and K meson pairs in two photon collisions is measured with ALEPH data collected between 1992 and 2000. Cross sections are presented as a function of cos σ∗ and invariant mass, for t|cosσ∗|< 0.6 and invariant masses between 2.0 and 6.0 GeV/c2) for pions (kaons). The shape of the distributions are found to be well described by QCD predictions but the data have a significantly higher normalisation.