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Journal articleBarate R, Buskulic D, Decamp D, et al., 1999,
Search for supersymmetry with a dominant R-parity violating <i>LQ(D)</i>over-bar coupling in e<SUP>+</SUP>e<SUP>-</SUP> collisions at centre-of-mass energies of 130 GeV to 172 GeV
, EUROPEAN PHYSICAL JOURNAL C, Vol: 7, Pages: 383-405, ISSN: 1434-6044- Cite
- Citations: 18
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Journal articleAbbiendi G, Ackerstaff K, Alexander G, et al., 1999,
Search for Higgs bosons in e<SUP>+</SUP>e<SUP>-</SUP> collisions at 183 GeV
, EUROPEAN PHYSICAL JOURNAL C, Vol: 7, Pages: 407-435, ISSN: 1434-6044- Cite
- Citations: 73
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Journal articleBarate R, Buskulic D, Decamp D, et al., 1999,
Search for B<sub>s</sub><SUP>0</SUP> oscillations using inclusive lepton events
, EUROPEAN PHYSICAL JOURNAL C, Vol: 7, Pages: 553-569, ISSN: 1434-6044- Cite
- Citations: 30
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Journal articleAbreu P, Adam W, Adye T, et al., 1999,
Search for lightest neutralino and stau pair production in light gravitino scenarios with stau NLSP
, EUROPEAN PHYSICAL JOURNAL C, Vol: 7, Pages: 595-607, ISSN: 1434-6044- Cite
- Citations: 7
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Journal articleAckerstaff K, Alexander G, Allison J, et al., 1999,
Measurements of flavour-dependent fragmentation functions in Z<SUP>0</SUP>→q(q)over-bar events
, EUROPEAN PHYSICAL JOURNAL C, Vol: 7, Pages: 369-381, ISSN: 1434-6044- Cite
- Citations: 74
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Journal articleAbreu P, Adam W, Adye T, et al., 1999,
Study of the four-jet anomaly observed at LEP centre-of-mass energies of 130 and 136 GeV
, PHYSICS LETTERS B, Vol: 448, Pages: 311-319, ISSN: 0370-2693- Cite
- Citations: 1
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Journal articleAcciarri M, Achard P, Adriani O, et al., 1999,
Measurement of the e<SUP>+</SUP>e<SUP>-</SUP>→Z→b(b)over-bar forward-backward asymmetry and the B<SUP>0</SUP>(B)over-bar<SUP>0</SUP> mixing parameter using prompt leptons
, PHYSICS LETTERS B, Vol: 448, Pages: 152-162, ISSN: 0370-2693- Cite
- Citations: 25
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Conference paperAlbergo S, Azzi P, Babucci E, et al., 1999,
Test results of heavily irradiated Si detectors
, 9th Symposium on Radiation Measurements and Applications, Publisher: ELSEVIER SCIENCE BV, Pages: 238-241, ISSN: 0168-9002 -
Journal articleBarate R, Buskulic D, Decamp D, et al., 1999,
Search for the standard model Higgs boson at the LEP2 collider near √<i>s</i>=183 GeV (vol 440, pg 403, 1998)
, PHYSICS LETTERS B, Vol: 447, Pages: 336-351, ISSN: 0370-2693- Cite
- Citations: 14
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Journal articleBarate R, Buskulic D, Decamp D, et al., 1999,
Analysis of transverse momentum correlations in hadronic Z decays
, PHYSICS LETTERS B, Vol: 447, Pages: 183-198, ISSN: 0370-2693 -
Journal articleAcciarri M, Achard P, Adriani O, et al., 1999,
The <i>Q</i><SUP>2</SUP> evolution of the hadronic photon structure function <i>F</i><sub>2</sub><SUP>γ</SUP> at LEP
, PHYSICS LETTERS B, Vol: 447, Pages: 147-156, ISSN: 0370-2693- Author Web Link
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- Citations: 50
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Journal articleAbbiendi G, Ackerstaff K, Alexander G, et al., 1999,
A measurement of the τ<SUP>-</SUP>→e<SUP>-</SUP>(ν)over-bar<sub>e</sub>ν<sub>τ</sub> branching ratio
, PHYSICS LETTERS B, Vol: 447, Pages: 134-146, ISSN: 0370-2693- Cite
- Citations: 20
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Journal articleAbbiendi G, Ackerstaff K, Alexander G, et al., 1999,
Search for baryon and lepton number violating Z<SUP>0</SUP> decays
, PHYSICS LETTERS B, Vol: 447, Pages: 157-166, ISSN: 0370-2693- Cite
- Citations: 5
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Journal articleAcciarri M, Adriani O, Aguilar-Benitez M, et al., 1999,
Search for charged Higgs bosons in e<SUP>+</SUP>e<SUP>-</SUP> collisions at centre-of-mass energies between 130 and 183 GeV
, PHYSICS LETTERS B, Vol: 446, Pages: 368-377, ISSN: 0370-2693- Author Web Link
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- Citations: 9
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Journal articleAbreu P, Adam W, Adye T, et al., 1999,
Search for charginos, neutralinos and gravitinos in e<SUP>+</SUP>e<SUP>-</SUP> interactions at √<i>s</i> = 183 GeV
, PHYSICS LETTERS B, Vol: 446, Pages: 75-91, ISSN: 0370-2693- Author Web Link
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- Citations: 24
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Journal articleAbreu P, Adam W, Adye T, et al., 1999,
Search for Leptoquarks and FCNC in <i>e</i><i><SUP>+</SUP></i><SUP>e</SUP><SUP>-</SUP> annihilations √<i>s</i> = 183 GeV
, PHYSICS LETTERS B, Vol: 446, Pages: 62-74, ISSN: 0370-2693- Author Web Link
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- Citations: 41
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Journal articleAcciarri M, Adriani O, Aguilar-Benitez M, et al., 1999,
Searches for scalar top and scalar bottom quarks in e<SUP>+</SUP>e<SUP>-</SUP> interactions at 161GeV≤√<i>s</i>≤183GeV
, PHYSICS LETTERS B, Vol: 445, Pages: 428-438, ISSN: 0370-2693- Cite
- Citations: 12
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Journal articleAcciarri M, Adriani O, Aguilar-Benitez M, et al., 1999,
Searches for scalar top and scalar bottom quarks in e+e- interactions at 161 GeV ≤ √s ≤ 183 GeV
, Physics Letters Section B Nuclear Elementary Particle and High Energy Physics, Vol: 445, Pages: 428-438, ISSN: 0370-2693Searches for scalar top and scalar bottom quarks have been performed at center-of-mass energies between 161 GeV and 183 GeV using the L3 detector at LEP. No signal is observed. Model-independent limits on production cross sections are determined for the two decay channels t̃<inf>1</inf> → cχ̃<sup>0</sup> <inf>1</inf> and b̃<inf>1</inf> → b χ̃<sup>0</sup> <inf>1</inf>. Within the framework of the Minimal Supersymmetric extension of the Standard Model mass limits are derived. For mass differences between t̃<inf>1</inf> and χ̃<sup>0</sup> <inf>1</inf> greater than 10 GeV a 95% C.L. limit of 81.5 GeV is set on the mass of the Supersymmetric partner of the left-handed top. A supersymmetric partner of the left-handed bottom with a mass below 80 GeV is excluded at 95% C.L. if the mass difference between b̃<inf>1</inf> and χ̃<inf>1</inf> is greater than 20 GeV. © 1999 Published by Elsevier Science B.V. All rights reserved.
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Journal articleAbbiendi G, Ackerstaff K, Alexander G, et al., 1999,
Bose-Einstein correlations in e+e- → W+W- at 172 and 183 GeV
, European Physical Journal C, Vol: 8, Pages: 559-571, ISSN: 1434-6044Bose-Einstein correlations between like-charge pions are studied in hadronic final states produced by e<sup>+</sup>e<sup>-</sup> annihilations at center-of-mass energies of 172 and 183 GeV. Three event samples are studied, each dominated by one of the processes W<sup>+</sup>W<sup>-</sup> →qq̄ℓν̄e, W<sup>+</sup>W<sup>-</sup> qq̄qq̄, or (Z<sup>0</sup>/γ)* → qq̄. After demonstrating the existence of Bose-Einstein correlations in W decays, an attempt is made to determine Bose-Einstein correlations for pions originating from the same W boson and from different W bosons, as well as for pions from (Z<sup>0</sup>/γ)* → qq̄ events. The following results are obtained for the individual chaoticity parameters λ, assuming a common source radius R: λ<sup>same</sup>= 0.63 ± 0.19 ± 0.14 λ<sup>diff</sup> = 0.22 ± 0.53 ±0.14, λ <sup>Z</sup>* = 0.47 ± 0.11 ± 0.08, R = 0.92 ± 0.09 ± 0.09 fm. In each case, the first error is statistical and the second is systematic. At the current level of statistical precision it is not established whether Bose-Einstein correlations, between pions from different W bosons exist or not.
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Journal articleAckerstaff K, Alexander G, Allison J, et al., 1999,
Production of K0S and Λ in quark and gluon jets from Z0 decay
, European Physical Journal C, Vol: 8, Pages: 241-254, ISSN: 1434-6044The production of K<sup>0</sup><inf>S</inf> mesons and Λ baryons in quark and gluon jets has been investigated using two complementary techniques. In the first approach, which provides high statistical accuracy, jets were selected using different jet finding algorithms and ordered according to their energy. Production rates were determined taking into account the dependences of quark and gluon compositions as a function of jet energy as predicted by Monte Carlo models. Selecting three-jet events with the k<inf>⊥</inf> (Durham) jet finder (Y<inf>cut</inf> = 0.005), the ratios of K<sup>0</sup><inf>S</inf> and Λ production rates in gluon and quark jets relative to the mean charged particle multiplicity were found to be 1.10 ± 0.02 ± 0.02 and 1.41 ± 0.04 ± 0.04, respectively, where the first uncertainty is statistical and the second is systematic. In the second approach, a new method of identifying quark jets based on the collimation of energy flow around the jet axis is introduced and was used to anti-tag gluon jets in symmetric (Y-shaped) three-jet events. Using the cone jet finding algorithm with a cone size of 30°, the ratios of relative production rates in gluon and quark jets were determined to be 0.94 ± 0.07 ± 0.07 for K<sup>0</sup><inf>S</inf> and 1.18 ± 0.10 ± 0.17 for Λ. The results of both analyses are compared to the predictions of Monte Carlo models.
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Journal articleAckerstaff K, Alexander G, Allison J, et al., 1999,
Measurements of flavour-dependent fragmentation functions in Z0 → qq̄ events
, European Physical Journal C, Vol: 7, Pages: 369-381, ISSN: 1434-6044Fragmentation functions for charged particles in Z<sup>0</sup> → qq̄ events have been measured for bottom (b), charm (c) and light (uds) quarks as well as for all flavours together. The results are based on data recorded between 1990 and 1995 using the OPAL detector at LEP. Event samples with different flavour compositions were formed using reconstructed D*<sup>±</sup> mesons and secondary vertices. The ξ<inf>P</inf> = ln(1/x<inf>p</inf>) distributions and the position of their maxima ξ<inf>0</inf> are also presented separately for uds, c and b quark events. The fragmentation function for b quarks is significantly softer than for uds quarks.
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Journal articleAcciarri M, Achard P, Adriani O, et al., 1999,
Study of Z boson pair production in e+e- colisions at LEP at √s = 189 GeV
, Physics Letters Section B Nuclear Elementary Particle and High Energy Physics, Vol: 465, Pages: 363-375, ISSN: 0370-2693The pair production of Z bosons is studied using the data collected by the L3 detector at LEP in 1998 in e<sup>+</sup>e<sup>-</sup> collisions at a centre-of-mass energy of 189 GeV. All the visible final states are considered and the cross section of this process is measured to be 0.74<inf>-0.14</inf> <sup>+0.15</sup>(stat.) ± 0.04(syst.)pb. Final states containing b quarks are enhanced by a dedicated selection and their production cross section is found to be 0.18<inf>-0.07</inf> <sup>+0.09</sup>(stat.) ± 0.02(syst.)pb. Both results are in agreement with the Standard Model predictions. Limits on anomalous couplings between neutral gauge bosons are derived from these measurements. © 1999 Published by Elsevier Science B.V. All rights reserved.
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Journal articleAcciarri M, Achard P, Adriani O, et al., 1999,
χc2 formation in two-photon collisions at LEP
, Physics Letters Section B Nuclear Elementary Particle and High Energy Physics, Vol: 453, Pages: 73-82, ISSN: 0370-2693Two-photon formation of the charmonium resonance χ<inf>c2</inf> has been studied with the L3 detector at LEP. The χ<inf>c2</inf> is identified through its decay χ<inf>c2</inf> → γJ/ψ with a subsequent decay J/ψ e<sup>-</sup> e<sup>-</sup> or J/ψ → e<sup>-</sup> e<sup>-</sup>. With an integrated luminosity of 140 pb<sup>-1</sup> at √s ≃ 91 GeV and 52 pb<sup>-1</sup> at √s ≃ 183 GeV, we measure the two-photon width of the χ<inf>c2</inf> to be Γ<inf>γγ</inf> = 1.02 ± 0.40 (stat.) ± 0.15 (sys.) ± 0.09(BR.)keV. © 1999 Published by Elsevier Science B.V. All rights reserved.
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Journal articleBarate R, Decamp D, Ghez P, et al., 1999,
A direct measurement of
, Physics Letters Section B Nuclear Elementary Particle and High Energy Physics, Vol: 465, Pages: 349-362, ISSN: 0370-2693The inclusive charm production rate in W decays is measured from a study of the properties of final state particles. The sample of W pairs is selected from 67.7 pb<sup>-1</sup>collected by ALEPH in 1996 and 1997 at centre-of-mass energies near 172 and 183 GeV in the channels W<sup>+</sup>W<sup>-</sup>→ 4q and W<sup>+</sup>W<sup>-</sup>→ℓvqq̄. The branching fraction of hadronic W decays to a final state containing a c quark, R<inf>c</inf> <sup>W</sup>= Γ(W→cX)/Γ(W→hadrons), is measured to be 0.51 ± 0.05<inf>stat</inf>+ 0.03<inf>syst.</inf>This allows a direct determination of the CKM matrix element |Vcs| = 1.00 ± 0.11<inf>stat</inf>± 0.07<inf>syst</inf>. © 1999 Published by Elsevier Science B.V. All rights reserved.
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Journal articleBarate R, Buskulic D, Decamp D, et al., 1999,
Search for the standard model Higgs boson at the LEP2 Collider near √s = 183 GeV
, Physics Letters Section B Nuclear Elementary Particle and High Energy Physics, Vol: 447, Pages: 336-351, ISSN: 0370-2693During 1997 the ALEPH experiment at LEP gathered 57pb<sup>-1</sup> of data at centre-of-mass energies near 183 GeV. These data are used to look for possible signals from the production of the Standard Model Higgs boson in the reaction e<sup>+</sup>e<sup>-</sup>→ HZ. No evidence of a signal is found in the data; seven events are selected, in agreement with the expectation of 7.2 events from background processes. This observation results in an improved lower limit on the mass of the Higgs boson: m<inf>H</inf> > 87.9GeV/c<sup>2</sup> at 95% confidence level. © 1999 Elsevier Science B.V. All rights reserved.
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Journal articleAbreu P, Adam W, Adye T, et al., 1999,
Measurements of the leptonic branching fractions of the tau
, European Physical Journal C, Vol: 10, Pages: 201-218, ISSN: 1434-6044Data collected with the DELPHI detector from 1993 to 1995 combined with previous DELPHI results for data from 1991 and 1992 yield the branching fractions B(τ → evv̄) = (17.877 ± 0.109<inf>stat</inf> ± 0.110<inf>sys</inf>)% and B(τ → μvv̄) = (17.325 ± 0.095<inf>stat</inf> ± 0.077<inf>sys</inf>)%.
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Journal articleAbreu P, Adam W, Adye T, et al., 1999,
A precise measurement of the partial decay width ratio Rb0 = Γbb̄/Γhad
, European Physical Journal C, Vol: 10, Pages: 415-442, ISSN: 1434-6044The partial decay width of the Z to bb̄ quark pairs has been measured by the DELPHI detector at LEP using data taken in the years 1992 to 1995. Decays of b-hadrons were tagged by several methods using tracks with large impact parameters and/or reconstructed secondary vertices, complemented by event shape variables. Combining these methods in a multivariate analysis the value Γ(Z → bb̄)/Γ(Z → had) = 0.21634 ± 0.00067 (stat) ± 0.00060 (syst) was obtained, where the cc̄ production fraction was fixed to its Standard Model value.
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Journal articleAndrés E, Askebjer P, Barwick SW, et al., 1999,
Status of the AMANDA experiment
, Nuclear Physics B Proceedings Supplements, Vol: 70, Pages: 448-452, ISSN: 0920-5632The AMANDA high energy neutrino telescope has successfully been increased in size from four detector strings to ten detector strings during the 1996/1997 season. The first upward going muon-neutrino candidates have been reconstructed from the 1996 year's four-string data. Three new detector strings will be deployed during 1997/1998 to 2350 metres depth.
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Journal articleFortunato E, Becker U, Dinner R, et al., 1999,
Systematic study of electron drift for gaseous chamber design
, IEEE Nuclear Science Symposium and Medical Imaging Conference, Vol: 1, Pages: 106-110We present a consistent set of measurements of electron drift velocities and Lorentz deflection angles in all noble gases with methane and ethane as quenchers in magnetic fields up to 0.8 Tesla. These and many other results are available in a searchable database on World Wide Web at http: //cyclotron.mit.edu/drift/ to allow for guided design and optimization of future detectors. A simple model is used to form an empirical parameterization of the results. This compact form unifies the drift characteristics of a gas mixture over a range of electric (0 - 1.5 kV/cm) and magnetic (0-0.8 Tesla) fields. A more detailed model is presented which explains the surprisingly large effect of even modest (and inevitable) nitrogen contamination on electron drift velocity. Additional measurements and simulations confirm the validity of the model's predictions and show possible applications.
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Journal articleScannavini MG, Speller RD, Royle GJ, et al., 1999,
Design of a small laboratory Compton camera for the imaging of positron emitters
, IEEE Nuclear Science Symposium and Medical Imaging Conference, Vol: 2, Pages: 1120-1126A small laboratory prototype has been designed for the Compton imaging of annihilation photons produced from positron emitters. Considerations on the design of the scatter collimator are presented and the system configuration is described. The system features a stack of four AC coupled, double-sided silicon strip detectors (6 × 6 cm<sup>2</sup> area, 500 μm thickness, 470 μm strip pitch, 128 channels/side) in a double Compton configuration and externally triggered readout mode. Signal readout is obtained by bonding two 128-channel low-noise APV6 chips to each detector. Custom electronics have been developed for the chip readout. The system is currently being assembled. The estimated angular resolution of the camera is approximately 4 degrees. High sensitivity could be achieved by extending the number of stack elements and by improving the design of the trigger detector, which presently consists of a small area germanium crystal.
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