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Journal articleBarate R, Buskulic D, Decamp D, et al., 1998,
Search for charged Higgs bosons in e<SUP>+</SUP>e<sub>-</sub> collisions at centre-of-mass energies from 130 to 172 GeV
, PHYSICS LETTERS B, Vol: 418, Pages: 419-429, ISSN: 0370-2693- Author Web Link
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- Citations: 20
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Journal articleAbreu P, Adam W, Adye T, et al., 1998,
Mb at Mz
, Physics Letters Section B Nuclear Elementary Particle and High Energy Physics, Vol: 418, Pages: 430-442, ISSN: 0370-2693The value of the b quark mass at the M<inf>2</inf> scale defined in the MS renormalization scheme, m<inf>b</inf>(M<inf>Z</inf>), was determined using 2.8 million hadronic Z decays collected during 1992-1994 by the DELPHI detector to be m<inf>b</inf>(M<inf>Z</inf>) = 2.67 ± 0.25 (stat.) ± 0.34 (frag.) ± 0.27 (theo.) GeV/c<sup>2</sup>. The analysis considers NLO corrections to the three-jet production rate including mass effects, and the result obtained agrees with the QCD prediction of having a running b quark mass at an energy scale equal to M<inf>Z</inf>. This is the first time that such a measurement is performed far above the bb̄ production threshold. The study also verifies the flavour independence of the strong coupling constant for b and light quarks within 1% accuracy. © 1998 Elsevier Science B.V.
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Journal articleAbreu P, Adam W, Adye T, et al., 1998,
m<sub>b</sub> at M<sub>Z</sub>
, PHYSICS LETTERS B, Vol: 418, Pages: 430-442, ISSN: 0370-2693- Author Web Link
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- Citations: 70
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Journal articleAckerstaff K, Alexander G, Allison J, et al., 1998,
Measurement of f(c→D*<SUP>+</SUP>,X), f(b→D*<SUP>+</SUP>,X) and Γ<sub>c(c)over-bar</sub>/Γ<sub>had</sub> using D*<SUP>±</SUP> mesons
, EUROPEAN PHYSICAL JOURNAL C, Vol: 1, Pages: 439-459, ISSN: 1434-6044- Author Web Link
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- Citations: 85
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Journal articleEnderby MD, Clarke AR, Patel M, et al., 1998,
An automated ultrasonic immersion technique for the determination of three-dimensional elastic constants of polymer composites
, ULTRASONICS, Vol: 36, Pages: 245-249, ISSN: 0041-624X- Author Web Link
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- Citations: 7
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Journal articleAckerstaff K, Alexander G, Allison J, et al., 1998,
Measurement of the W boson mass and W<SUP>+</SUP>W<SUP>-</SUP> production and decay properties in e<SUP>+</SUP>e<SUP>-</SUP> collisions at √s = 172 GeV
, EUROPEAN PHYSICAL JOURNAL C, Vol: 1, Pages: 395-424, ISSN: 1434-6044- Cite
- Citations: 53
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Journal articleAckerstaff K, Alexander G, Allison J, et al., 1998,
Search for the standard model Higgs boson in e<SUP>+</SUP>e<SUP>-</SUP> collisions at √s=161-172 GeV
, EUROPEAN PHYSICAL JOURNAL C, Vol: 1, Pages: 425-438, ISSN: 1434-6044- Author Web Link
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- Citations: 37
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Journal articleBarate R, Buskulic D, Decamp D, et al., 1998,
Studies of quantum chromodynamics with the ALEPH detector
, PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS, Vol: 294, Pages: 2-165, ISSN: 0370-1573- Cite
- Citations: 244
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Journal articleAckerstaff K, Alexander G, Allison J, et al., 1998,
Multiplicity distributions of gluon and quark jets and tests of QCD analytic predictions
, EUROPEAN PHYSICAL JOURNAL C, Vol: 1, Pages: 479-494, ISSN: 1434-6044- Cite
- Citations: 57
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Journal articleAckerstaff K, Alexander G, Allison J, et al., 1998,
Investigation of CP violation in B0 → J/ψKS0 decays at LEP
, European Physical Journal C, Vol: 5, Pages: 379-388, ISSN: 1434-6044An investigation of CP violation was performed using a total of 24 candidates for B<sup>0</sup> → J/ψK<sup>0</sup><inf>S</inf> decay, with a purity of about 60%. These events were selected from 4.4 million hadronic Z<sup>0</sup> decays recorded by the OPAL detector at LEP. An analysis procedure, involving techniques to reconstruct the proper decay times and tag the produced b-flavours, B<sup>0</sup> or B̄<sup>0</sup>, has been developed to allow a first direct study of the time dependent CP asymmetry that, in the Standard Model, is sin 2β. The result is sin 2β = 3.2<sup>+1.8</sup> <inf>-2.0</inf> ± 0.5 where the first error is statistical and the second systematic. This result is used to determine probabilities for different values of sin 2β in the physical region from -1 to +1.
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Journal articleAckerstaff K, Alexander G, Allison J, et al., 1998,
An upper limit for the τ-neutrino mass from τ → 5π±vτ decays
, European Physical Journal C, Vol: 5, Pages: 229-237, ISSN: 1434-6044An upper limit for the τ-neutrino mass has been determined from the decay τ → 5π<sup>±</sup>v<inf>τ</inf> using data collected with the OPAL detector from 1991 to 1995 in e<sup>+</sup>e<sup>-</sup> collisions at √s ≈ Mz. A limit of 43.2 MeV at 95% CL is obtained using a two-dimensional method in the 5π invariant mass and energy distribution from 22 selected events. Combining this result with OPAL's previously published measurement using τ<sup>+</sup> τ<sup>-</sup> → 3h<sup>±</sup>v̄<inf>τ</inf> + 3h∓v<inf>τ</inf> decays, a new combined limit of m<inf>vτ</inf> < 27.6 MeV (95% CL) is obtained.
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Journal articleAckerstaff K, Alexander G, Allison J, et al., 1998,
Search for anomalous production of di-lepton events with missing transverse momentum in e+e- collisions at √S = 161 and 172 GeV
, European Physical Journal C, Vol: 4, Pages: 47-74, ISSN: 1434-6044Events containing two charged leptons and significant missing transverse momentum are selected from a data sample corresponding to a total integrated luminosity of 20.6 pb<sup>-1</sup> at centre-of-mass energies of 161 GeV and 172 GeV. The observed number of events, four at 161 GeV and nine at 172 GeV, is consistent with the number expected from Standard Model processes, predominantly arising from W<sup>+</sup>W<sup>-1</sup> production with each W decaying leptonically. This topology is also an experimental signature for the pair production of new particles that decay to a charged lepton accompanied by one or more invisible particles Further event selection criteria are described that optimise the sensitivity to particular new physics channels No evidence for new phenomena is observed and limits on the production of scalar charged lepton pairs and other new particles are presented.
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Journal articleAckerstaff K, Alexander G, Allison J, et al., 1998,
A measurement of the B0s lifetime using reconstructed D-s mesons
, European Physical Journal C, Vol: 2, Pages: 407-416, ISSN: 1434-6044We report a measurement of the B<sup>0</sup><inf>s</inf> meson lifetime from B<sup>0</sup><inf>s</inf> → D<sup>-</sup><inf>s</inf>X decays, where D<sup>-</sup><inf>s</inf> mesons are reconstructed in the D<sup>-</sup><inf>s</inf> → φπ<sup>-</sup> and D<sup>-</sup><inf>s</inf> → K*<sup>0</sup>K<sup>-</sup> decay channels. From approximately 3.7 million hadronic Z<sup>0</sup> decays recorded by the OPAL detector at LEP a sample is selected containing 911 ± 83 candidates, of which 519 ± 136 are estimated to be from B<sup>0</sup><inf>s</inf> meson decays. Fitting the distribution of the distance from the beam spot to the decay vertex of the D<sup>-</sup><inf>s</inf> candidates with an unbinned likelihood function we measure π(B<sup>0</sup><inf>s</inf>) = 1 72<sup>+0.20+0.18</sup><inf>-0.19-0.17</inf> ps, where the errors are statistical and systematic, respectively.
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Journal articleAcciarri M, Adriani O, Aguilar-Benitez M, et al., 1998,
Measurement of the B0d - B̄0d oscillation frequency
, European Physical Journal C, Vol: 5, Pages: 195-203, ISSN: 1434-6044Time-dependent B<sup>0</sup>-B̄<sup>0</sup> mixing is studied using about two million hadronic Z decays registered by L3 in 1994 and 1995. For this study three techniques are used. Tagging of the b-quark charge at decay time is performed by identifying leptons from semileptonic B decays. The flavour of the b quark at production time is determined from the charge of the lepton in the opposite hemisphere or by using a jet-charge technique. The proper time of the B-particle decay is obtained by reconstructing the production and decay vertices or by a measurement of the lepton impact parameter. The combined result for the frequency of B<sup>0</sup><inf>d</inf> meson oscillations is Δm<inf>d</inf> = 0.444 ± 0.040 ps<sup>-1</sup>.
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Journal articleBarate R, Buskulic D, Decamp D, et al., 1998,
K0 S production in τ decays
, European Physical Journal C, Vol: 4, Pages: 29-45, ISSN: 1434-6044From a sample of about 160k Z → τ<sup>+</sup>τ<sup>-</sup> candidates collected with the ALEPH detector at LEP between 1991 and 1995, τ lepton decays involving K<sup>0</sup> <inf>S</inf> → π<sup>+</sup>π<sup>-</sup> are studied. The K<sup>0</sup> <inf>S</inf>K<sup>0</sup> <inf>L</inf> associated production in τ decays is also investigated. The branching ratios are measured for the inclusive decay B(τ<sup>-</sup>→K<sup>0</sup> <inf>S</inf>X<sup>-</sup>ν <inf>τ</inf>) = (9.70±0.58±0.62) × 10<sup>-3</sup>, where X<sup>-</sup> can be anything, and for the exclusive decays B(τ<sup>-</sup>→K̄<sup>0</sup>π<sup>-</sup>ν <inf>τ</inf>) = (8.55±1.17±0.66) × 10<sup>-3</sup>, B(τ<sup>-</sup>→K̄<sup>0</sup>π<sup>-</sup>π <sup>0</sup>ν<inf>τ</inf>) = (2.94±0.73±0.37) × 10<sup>-3</sup>, B(τ<sup>-</sup>→K̄<sup>0</sup>K<sup>-</sup>ν<inf>τ</inf>) = (1.58±0.42±0.17) × 10<sup>-3</sup>, B(τ<sup>-</sup>→K̄<sup>0</sup>K<sup>-</sup>π <sup>0</sup>ν<inf>τ</inf>) = (1.52±0.76±0.21) × 10<sup>-3</sup>. The decay τ<sup>-</sup>→K<sup>0</sup> <inf>S</inf>K<sup>0</sup> <inf>L</inf>π<sup>-</sup>ν<inf>τ</inf> is studied for the first time, giving a branching ratio B(τ<sup>-</sup>→K<sup>0</sup
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Journal articleAbreu P, Adam W, Adye T, et al., 1998,
π±, K±, p and p̄ production in Z0 → qq̄, Z0 bb̄, Z0 → uū, dd̄, ss̄
, European Physical Journal C, Vol: 5, Pages: 585-620, ISSN: 1434-6044The DELPHI experiment at LEP uses Ring Imaging Cherenkov detectors for particle identification. The good understanding of the RICH detectors allows the identification of charged pions, kaons and protons, covering the full momentum range from 0.7 < p < 45.6GeV/c. The π<sup>±</sup>, K<sup>±</sup>, p and p̄ normalised production rates, their differential cross sections, multiplicities and the maxima ξ*<inf>p</inf> of_the ξ<inf>p</inf> = ln (1/X<inf>p</inf>) distributions are measured for three event samples Z<sup>0</sup> → qq̄, Z<sup>0</sup> → bb̄, Z<sup>0</sup> → uū, dd̄, ss̄, selected from ∼ 1 400 000 Z<inf>0</inf> decays collected by DELPHI in 1994. The results are compared to the predictions of the JETSET string fragmentation model and the HERWIG cluster fragmentation model. The Modified Leading Logarithm Approximation with Local Parton-Hadron Duality is tested. The ξ*<inf>p</inf> dependence on the primary quark flavour is investigated and quantified for the different particle distributions. The π<sup>±</sup> , K<sup>±</sup>, p and p̄ multiplicities are measured with precisions from ±4% to ±6%. Forche Z<sup>0</sup> → qq̄, and Z<sup>0</sup> → bb̄, event samples, these improve on previous measurements. The π<sup>±</sup>, K<sup>±</sup>, p and p̄ multiplicities for Z<sup>0</sup> → uū, dd̄, ss̄ are presented for the first time.
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Journal articleBarate R, Buskulic D, Decamp D, et al., 1998,
Studies of quantum chromodynamics with the ALEPH detector
, Physics Report, Vol: 294, Pages: 1-165, ISSN: 0370-1573Previously published and as yet unpublished QCD results obtained with the ALEPH detector at LEP1 are presented. The unprecedented statistics allows detailed studies of both perturbative and non-perturbative aspects of strong interactions to be carried out using hadronic Z and tau decays. The studies presented include precise determinations of the strong coupling constant, tests of its flavour independence, tests of the SU(3) gauge structure of QCD, study of coherence effects, and measurements of single-particle inclusive distributions and two-particle correlations for many identified baryons and mesons. © 1998 Elsevier Science B.V.
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Journal articleAraüjo HM, 1998,
Study of bialkali photocathodes below room temperature in the uv/vuv region
, IEEE Transactions on Nuclear Science, Vol: 45, Pages: 542-549, ISSN: 0018-9499Two photomultiplier tubes with bialkali photocathodes and fused silica windows (2″ Philips XP2020Q and 1-1/8" Hamamatsu R1668) were studied between room temperature and -160°C, illuminated in dc mode in the UV/VUV wavelength range. The photomultipliers were operated as diodes, with direct measurement of the current of photoelectrons, in order to study in detail the effects associated to the photocathode. The influence of light intensity, applied voltage and illuminated area on the response as a function of temperature were investigated. The increase of the electrical resistivity of the emissive layer upon cooling proved to be responsible for a loss of linearity of the photocathode response, leading ultimately to the complete absence of signal at low temperature. A simplified model is presented that accounts for some experimental results. An unexpected increase of response below room temperature was also found at 170 nm. © 1998 IEEE.
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Journal articleAbreu P, Adam W, Adye T, et al., 1998,
Charged particle multiplicity in e<SUP>+</SUP>e<SUP>-</SUP>→q(q)over-bar events at 161 and 172 GeV and from the decay of the W boson
, PHYSICS LETTERS B, Vol: 416, Pages: 233-246, ISSN: 0370-2693- Cite
- Citations: 36
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Journal articleAbreu P, Adam W, Adye T, et al., 1998,
Rapidity correlations in Λ baryon and proton production in hadronic Z<SUP>0</SUP> decays
, PHYSICS LETTERS B, Vol: 416, Pages: 247-256, ISSN: 0370-2693- Author Web Link
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- Citations: 14
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Journal articleAcciarri M, Adriani O, Aguilar-Benitez M, et al., 1998,
Measurement of the average lifetime of b-hadrons in Z decays
, PHYSICS LETTERS B, Vol: 416, Pages: 220-232, ISSN: 0370-2693- Author Web Link
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- Citations: 11
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Journal articleAbreu P, Adam W, Adye T, et al., 1998,
Search for charginos, neutralinos and gravitinos at LEP
, EUROPEAN PHYSICAL JOURNAL C, Vol: 1, Pages: 1-20, ISSN: 1434-6044- Author Web Link
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- Citations: 41
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Journal articleAckerstaff K, Alexander G, Allison J, et al., 1998,
Multi-photon final states in e<SUP>+</SUP>e<SUP>-</SUP> collisions at √s=130-172 GeV
, EUROPEAN PHYSICAL JOURNAL C, Vol: 1, Pages: 21-30, ISSN: 1434-6044- Cite
- Citations: 12
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Journal articleBarate R, Buskulic D, Decamp D, et al., 1998,
Three-prong τ decays with charged kaons
, EUROPEAN PHYSICAL JOURNAL C, Vol: 1, Pages: 65-79, ISSN: 1434-6044- Cite
- Citations: 35
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Journal articleAckerstaff K, Alexander G, Allison J, et al., 1998,
Search for a massive Di-photon resonance at √s=91-172 GeV
, EUROPEAN PHYSICAL JOURNAL C, Vol: 1, Pages: 31-43, ISSN: 1434-6044- Cite
- Citations: 16
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Journal articleAckerstaff K, Alexander G, Allison J, et al., 1998,
Search for unstable heavy and excited leptons in e<SUP>+</SUP>e<SUP>-</SUP> collisions at √s=170-172 GeV
, EUROPEAN PHYSICAL JOURNAL C, Vol: 1, Pages: 45-64, ISSN: 1434-6044- Cite
- Citations: 23
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Journal articleAckerstaff et al K, 1998,
Measurement of the one-prong hadronic tau branching ratios at LEP
, The European Physical Journal C, Vol: 4, Pages: 193-193, ISSN: 1434-6044 -
Journal articleAckerstaff et al K, 1998,
A search for neutral Higgs bosons in the MSSM and models with two scalar field doublets
, The European Physical Journal C, Vol: 5, Pages: 19-19, ISSN: 1434-6044 -
Journal articleAckerstaff et al K, 1998,
Search for a massive Di-photon resonance at
, The European Physical Journal C, Vol: 1, Pages: 31-31, ISSN: 1434-6044 -
Journal articleAckerstaff et al K, 1998,
Photon and light meson production in hadronic Z
, The European Physical Journal C, Vol: 5, Pages: 411-411, ISSN: 1434-6044
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