| 1. |
- Schael, S., et al.
(author)
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Electroweak measurements in electron positron collisions at W-boson-pair energies at LEP
- 2013
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In: Physics Reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 532:4, s. 119-244
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Research review (peer-reviewed)abstract
- Electroweak measurements performed with data taken at the electron positron collider LEP at CERN from 1995 to 2000 are reported. The combined data set considered in this report corresponds to a total luminosity of about 3 fb(-1) collected by the four LEP experiments ALEPH, DELPHI, 13 and OPAL, at centre-of-mass energies ranging from 130 GeV to 209 GeV. Combining the published results of the four LEP experiments, the measurements include total and differential cross-sections in photon-pair, fermion-pair and four-fermion production, the latter resulting from both double-resonant WW and ZZ production as well as singly resonant production. Total and differential cross-sections are measured precisely, providing a stringent test of the Standard Model at centre-of-mass energies never explored before in electron positron collisions. Final-state interaction effects in four-fermion production, such as those arising from colour reconnection and Bose Einstein correlations between the two W decay systems arising in WW production, are searched for and upper limits on the strength of possible effects are obtained. The data are used to determine fundamental properties of the W boson and the electroweak theory. Among others, the mass and width of the W boson, m(w) and Gamma(w), the branching fraction of W decays to hadrons, B(W -> had), and the trilinear gauge-boson self-couplings g(1)(Z), K-gamma and lambda(gamma), are determined to be: m(w) = 80.376 +/- 0.033 GeV Gamma(w) = 2.195 +/- 0.083 GeV B(W -> had) = 67.41 +/- 0.27% g(1)(Z) = 0.984(-0.020)(+0.018) K-gamma - 0.982 +/- 0.042 lambda(gamma) = 0.022 +/- 0.019. (C) 2013 Elsevier B.V. All rights reserved.
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| 2. |
- Schael, S, et al.
(author)
-
Precision electroweak measurements on the Z resonance
- 2006
-
In: Physics Reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 427:5-6, s. 257-454
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Research review (peer-reviewed)abstract
- We report on the final electroweak measurements performed with data taken at the Z resonance by the experiments operating at the electron-positron colliders SLC and LEP. The data consist of 17 million Z decays accumulated by the ALEPH, DELPHI, L3 and OPAL experiments at LEP, and 600 thousand Z decays by the SLID experiment using a polarised beam at SLC. The measurements include cross-sections, forward-backward asymmetries and polarised asymmetries. The mass and width of the Z boson, m(Z) and Gamma(Z), and its couplings to fermions, for example the p parameter and the effective electroweak mixing angle for leptons, are precisely measured: m(Z) = 91.1875 +/- 0.0021 GeV, Gamma(Z) = 2.4952 +/- 0.0023 GeV, rho(l) = 1.0050 +/- 0.0010, sin(2)theta(eff)(lept) = 0.23153 +/- 0.00016. The number of light neutrino species is determined to be 2.9840 +/- 0.0082, in agreement with the three observed generations of fundamental fermions. The results are compared to the predictions of the Standard Model (SM). At the Z-pole, electroweak radiative corrections beyond the running of the QED and QCD coupling constants are observed with a significance of five standard deviations, and in agreement with the Standard Model. Of the many Z-pole measurements, the forward-backward asymmetry in b-quark production shows the largest difference with respect to its SM expectation, at the level of 2.8 standard deviations. Through radiative corrections evaluated in the framework of the Standard Model, the Z-pole data are also used to predict the mass of the top quark, m(t) = 173(+10)(+13) GeV, and the mass of the W boson, m(W) = 80.363 +/- 0.032 GeV. These indirect constraints are compared to the direct measurements, providing a stringent test of the SM. Using in addition the direct measurements of m(t) and m(W), the mass of the as yet unobserved SM Higgs boson is predicted with a relative uncertainty of about 50% and found to be less than 285 GeV at 95% confidence level. (c) 2006 Elsevier B.V. All rights reserved.
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| 3. |
- Fomalont, E. B., et al.
(author)
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THE 2014 ALMA LONG BASELINE CAMPAIGN: AN OVERVIEW
- 2015
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In: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 808:1
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Journal article (peer-reviewed)abstract
- A major goal of the Atacama Large Millimeter/submillimeter Array (ALMA) is to make accurate images with resolutions of tens of milliarcseconds, which at submillimeter (submm) wavelengths requires baselines up to similar to 15 km. To develop and test this capability, a Long Baseline Campaign (LBC) was carried out from 2014 September to late November, culminating in end-to-end observations, calibrations, and imaging of selected Science Verification (SV) targets. This paper presents an overview of the campaign and its main results, including an investigation of the short-term coherence properties and systematic phase errors over the long baselines at the ALMA site, a summary of the SV targets and observations, and recommendations for science observing strategies at long baselines. Deep ALMA images of the quasar 3C 138 at 97 and 241 GHz are also compared to VLA 43 GHz results, demonstrating an agreement at a level of a few percent. As a result of the extensive program of LBC testing, the highly successful SV imaging at long baselines achieved angular resolutions as fine as 19 mas at similar to 350 GHz. Observing with ALMA on baselines of up to 15 km is now possible, and opens up new parameter space for submm astronomy.
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| 4. |
- Abreu, P., et al.
(author)
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Measurement of the gluon fragmentation function and a comparison of the scaling violation in gluon and quark jets
- 2000
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In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 13:4, s. 573-589
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Journal article (peer-reviewed)abstract
- The fragmentation functions of quarks and gluons are measured in various three-jet topologies in Z decays from the full data set collected with the DELPHI detector at the Z resonance between 1992 and 995. The results at different values of transverse momentum-like scales are compared. A parameterization of the quark and gluon fragmentation functions at a fixed reference scale is given. The quark and gluon fragmentation functions show the predicted pattern of scaling violations. The scaling violation for quark jets as a function of a transverse momentum-like scale is in a good agreement with that observed in lower energy e+e- annihilation experiments. For gluon jets it appears to be significantly stronger. The scale dependences of the gluon and quark fragmentation functions agree with the prediction of the DGLAP evolution equations from which the colour factor ratio CA/CF is measured to be: CA/CF = 2.26 ± 0.09stat. ± 0.06sys. ± 0.12clus.,scale..
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| 5. |
- Abreu, P., et al.
(author)
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Study of dimuon production in photon-photon collisions and measurement of QED photon structure functions at LEP
- 2001
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In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 19:1, s. 15-28
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Journal article (peer-reviewed)abstract
- Muon pair production in the process e+e- → e+e- μ+μ- is studied using the data taken at LEP1 (√s ≃ mz) with the DELPHI detector during the years 1992-1995. The corresponding integrated luminosity is 138.5 pb-1. The QED predictions have been tested over the whole Q2 range accessible at LEP1 (from several GeV2/c4 to several hundred GeV2/c4) by comparing experimental distributions with distributions resulting from Monte Carlo simulations using various generators. Selected events are used to extract the leptonic photon structure function Fγ 2. Azimuthal correlations are used to obtain information on additional structure functions, Fγ A and Fγ B, which originate from interference terms of the scattering amplitudes. The measured ratios Fγ A/Fγ 2 and FγB/Fγ 2 are significantly different from zero and consistent with QED predictions.
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| 6. |
- Abreu, P., et al.
(author)
-
Search for sleptons in e+e- collisions at √s = 183 to 189 GeV
- 2001
-
In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 19:1, s. 29-42
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Journal article (peer-reviewed)abstract
- Data taken by the DELPHI experiment at centre-of-mass energies of 183 GeV and 189 GeV with a total integrated luminosity of 212 pb-1 have been used to search for the supersymmetric partners of the electrons, muons, and taus in the context of the Minimal Supersymmetric Standard Model (MSSM). The decay topologies searched for were the direct decay (ℓ̃ → ℓx̃), producing acoplanar lepton pairs plus missing energy, and the cascade decay (ℓ → ℓx̃0 2 → ℓγx̃0 1), producing acoplanar lepton and photon pairs plus missing energy. The observed number of events is in agreement with Standard Model predictions. The 95% CL excluded mass limits for selectrons, smuons and staus are mẽ ≤ 87 GeV/c2, mμ̃ ≤ 80 GeV/c2 and mτ̃ 75 GeV/c2, respectively, for values of μ=-200 GeV/c2 and tanβ=1.5.
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| 7. |
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| 8. |
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| 9. |
- Pantazis, N, et al.
(author)
-
Determining the likely place of HIV acquisition for migrants in Europe combining subject-specific information and biomarkers data
- 2019
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In: Statistical methods in medical research. - : SAGE Publications. - 1477-0334 .- 0962-2802. ; 28:7, s. 1979-1997
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Journal article (peer-reviewed)abstract
- In most HIV-positive individuals, infection time is only known to lie between the time an individual started being at risk for HIV and diagnosis time. However, a more accurate estimate of infection time is very important in certain cases. For example, one of the objectives of the Advancing Migrant Access to Health Services in Europe (aMASE) study was to determine if HIV-positive migrants, diagnosed in Europe, were infected pre- or post-migration. We propose a method to derive subject-specific estimates of unknown infection times using information from HIV biomarkers’ measurements, demographic, clinical, and behavioral data. We assume that CD4 cell count (CD4) and HIV-RNA viral load trends after HIV infection follow a bivariate linear mixed model. Using post-diagnosis CD4 and viral load measurements and applying the Bayes’ rule, we derived the posterior distribution of the HIV infection time, whereas the prior distribution was informed by AIDS status at diagnosis and behavioral data. Parameters of the CD4–viral load and time-to-AIDS models were estimated using data from a large study of individuals with known HIV infection times (CASCADE). Simulations showed substantial predictive ability (e.g. 84% of the infections were correctly classified as pre- or post-migration). Application to the aMASE study ( n = 2009) showed that 47% of African migrants and 67% to 72% of migrants from other regions were most likely infected post-migration. Applying a Bayesian method based on bivariate modeling of CD4 and viral load, and subject-specific information, we found that the majority of HIV-positive migrants in aMASE were most likely infected after their migration to Europe.
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| 10. |
- Abdallah, J., et al.
(author)
-
A study of the b-quark fragmentation function with the DELPHI detector at LEP I and an averaged distribution obtained at the Z Pole
- 2011
-
In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 71:2, s. 1557-
-
Journal article (peer-reviewed)abstract
- The nature of b-quark jet hadronisation has been investigated using data taken at the Z peak by the DELPHI detector at LEP. Two complementary methods are used to reconstruct the energy of weakly decaying b-hadrons, E-B(weak). The average value of x(B)(weak) = E-B(weak)/E-beam is measured to be 0.699 +/- 0.011. The resulting x(B)(weak) distribution is then analysed in the framework of two choices for the perturbative contribution (parton shower and Next to Leading Log QCD calculation) in order to extract measurements of the non-perturbative contribution to be used in studies of b-hadron production in other experimental environments than LEP. In the parton shower framework, data favour the Lund model ansatz and corresponding values of its parameters have been determined within PYTHIA 6.156 from DELPHI data: a = 1.84(-0.21)(+0.23) and b = 0.642(-0.063)(+0.073) GeV-2, with a correlation factor rho = 92.2%. Combining the data on the b-quark fragmentation distributions with those obtained at the Z peak by ALEPH, OPAL and SLD, the average value of x(B)(weak) is found to be 0.7092 +/- 0.0025 and the non-perturbative fragmentation component is extracted. Using the combined distribution, a better determination of the Lund parameters is also obtained: a = 1.48(-0.10)(+0.11) and b = 0.509(-0.023)(+0.024) GeV-2, with a correlation factor rho = 92.6%.
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| 11. |
- Abdallah, J., et al.
(author)
-
Di-jet production in gamma gamma collisions at LEP2
- 2008
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In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; C:58, s. 531-541
-
Journal article (peer-reviewed)
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| 12. |
- Abdallah, J., et al.
(author)
-
Measurement of the electron structure function F-2(e) at LEP energies
- 2014
-
In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 737, s. 39-47
-
Journal article (peer-reviewed)abstract
- The hadronic part of the electron structure function F-2(e) has been measured for the first time, using e(+)e(-) data collected by the DELPHI experiment at LEP, at centre-of-mass energies of root s = 91.2-209.5 GeV. The data analysis is simpler than that of the measurement of the photon structure function. The electron structure function F-2(e) data are compared to predictions of phenomenological models based on the photon structure function. It is shown that the contribution of large target photon virtualities is significant. The data presented can serve as a cross-check of the photon structure function F-2(gamma) analyses and help in refining existing parameterisations.
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| 13. |
- Abdallah, J., et al.
(author)
-
Measurement of the tau lepton polarisation at LEP2
- 2008
-
In: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 659:1-2, s. 65-73
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Journal article (peer-reviewed)abstract
- A first measurement of the average polarisation P-tau of tau leptons produced in e(+)e(-) annihilation at energies significantly above the Z resonance is presented. The polarisation is determined from the kinematic spectra of tau hadronic decays. The measured value P-tau = -0.164 +/- 0.125 is consistent with the Standard Model prediction for the mean LEP energy of 197 GeV. (c) 2007 Elsevier B.V. All rights reserved.
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| 14. |
- Abdallah, J., et al.
(author)
-
Measurements of CP-conserving trilinear gauge boson couplings WWV (V gamma, Z) in e(+)e(-) collisions at LEP2
- 2010
-
In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 66:1-2, s. 35-56
-
Journal article (peer-reviewed)abstract
- The data taken by DELPHI at centre-of-mass energies between 189 and 209 GeV are used to place limits on the CP-conserving trilinear gauge boson couplings Delta g(1)(Z), lambda(gamma) and Delta k(gamma) associated to W+W- and single W production at LEP2. Using data from the jjl nu, jjjj, jjX and lX final states, where j,l and X represent a jet, a lepton and missing four-momentum, respectively, the following limits are set on the couplings when one parameter is allowed to vary and the others are set to their Standard Model values of zero: Delta g(1)(Z) =-0.025-(+0.033)(0.030,), lambda(gamma) = 0.002(-0.035)(+0.035) and Delta k(gamma) = 0.024(-0.081)(+0.077). Results are also presented when two or three parameters are allowed to vary. All observations are consistent with the predictions of the Standard Model and supersede the previous results on these gauge coupling parameters published by DELPHI.
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| 15. |
- Abdallah, J., et al.
(author)
-
Search for one large extra dimension with the DELPHI detector at LEP
- 2009
-
In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 60:1, s. 17-23
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Journal article (peer-reviewed)abstract
- Single photons detected by the DELPHI experiment at LEP2 in the years 1997-2000 are reanalysed to investigate the existence of a single extra dimension in a modified ADD scenario with slightly warped large extra dimensions. The data collected at centre-of-mass energies between 180 and 209 GeV for an integrated luminosity of similar to 650 pb(-1) agree with the predictions of the Standard Model and allow a limit to be set on graviton emission in one large extra dimension. The limit obtained on the fundamental mass scale M-D is 1.69 TeV/c(2) at 95% CL, with an expected limit of 1.71 TeV/c(2).
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| 16. |
- Abdallah, J., et al.
(author)
-
Search for single top quark production via contact interactions at LEP2
- 2011
-
In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 71:2, s. 1555-
-
Journal article (peer-reviewed)abstract
- Single top quark production via four-fermion contact interactions associated to flavour-changing neutral currents was searched for in data taken by the DELPHI detector at LEP2. The data were accumulated at centre-of-mass energies ranging from 189 to 209 GeV, with an integrated luminosity of 598.1 pb(-1). No evidence for a signal was found. Limits on the energy scale Lambda, were set for scalar-, vector- and tensor-like coupling scenarios.
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| 17. |
- Abdallah, J., et al.
(author)
-
Study of the dependence of direct soft photon production on the jet characteristics in hadronic Z (0) decays
- 2010
-
In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 67:3-4, s. 343-366
-
Journal article (peer-reviewed)abstract
- An analysis of the direct soft photon production rate as a function of the parent jet characteristics is presented, based on hadronic events collected by the DELPHI experiment at LEP1. The dependences of the photon rates on the jet kinematic characteristics (momentum, mass, etc.) and on the jet charged, neutral and total hadron multiplicities are reported. Up to a scale factor of about four, which characterizes the overall value of the soft photon excess, a similarity of the observed soft photon behavior to that of the inner hadronic bremsstrahlung predictions is found for the momentum, mass, and jet charged multiplicity dependences. However for the dependence of the soft photon rate on the jet neutral and total hadron multiplicities a prominent difference is found for the observed soft photon signal as compared to the expected bremsstrahlung from final state hadrons. The observed linear increase of the soft photon production rate with the jet total hadron multiplicity and its strong dependence on the jet neutral multiplicity suggest that the rate is proportional to the number of quark pairs produced in the fragmentation process, with the neutral pairs being more effectively radiating than the charged ones.
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| 18. |
- Abdallah, J., et al.
(author)
-
A determination of the centre-of-mass energy at LEP2 using radiative two-fermion events
- 2006
-
In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 46:2, s. 295-305
-
Journal article (peer-reviewed)abstract
- Using e(+)e(-) -> mu(+)mu(-)(gamma) and e(+)e(-) -> q (q) over bar(gamma) events radiative to the Z pole, DELPHI has determined the centre-of-mass energy, root s, using energy and momentum constraint methods. The results are expressed as deviations from the nominal LEP centre-of-mass energy, measured using other techniques. The results are found to be compatible with the LEP Energy Working Group estimates for a combination of the 1997 to 2000 data sets.
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| 19. |
- Abdallah, J., et al.
(author)
-
A study of b(b)over-bar production in e(+)e(-) collisions at root s=130-207 GeV
- 2009
-
In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 60:1, s. 1-15
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Journal article (peer-reviewed)abstract
- Measurements are presented of R-b, the ratio of the b (b) over bar cross-section to the q (q) over bar cross-section in e(+)e(-) collisions, and the forward-backward asymmetry A(FB)(b) at twelve energy points in the range root s = 130-207 GeV. These results are found to be consistent with the Standard Model expectations. The measurements are used to set limits on new physics scenarios involving contact interactions.
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| 20. |
- Abdallah, J., et al.
(author)
-
Measurement of the mass and width of the W boson in e(+) e(-) collisions at root s=161-209 GeV
- 2008
-
In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; C:55, s. 1-38
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Journal article (peer-reviewed)abstract
- A measurement of the W boson mass and width has been performed by the DELPHI collaboration using the data collected during the full LEP2 programme (1996-2000). The data sample has an integrated luminosity of 660 pb(-1) and was collected over a range of centre-of-mass energies from 161 to 209 GeV. Results are obtained by applying the method of direct reconstruction of the mass of the W from its decay products in both the W+W- -> l (nu) over bar (l) and W+W- -> q (q) over bar'(q) over barq'channels. The W mass result for the combined data set is M-W = 80.336 +/- 0.055(Stat.) +/- 0.028(Syst.) +/- 0.025(FSI) +/- 0.009(LEP) GeV/c(2) , where FSI represents the uncertainty due to final state interaction effects in the q (q) over bar'(q) over barq' channel, and LEP represents that arising from the knowledge of the collision energy of the accelerator. The combined value for the W width is Gamma(W) = 2.404 +/- 0.140(Stat.) +/- 0.077(Syst.) +/- 0.065(FSI) GeV/c(2). These results supersede all values previously published by the DELPHI collaboration.
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| 21. |
- Abdallah, J., et al.
(author)
-
Search for a fourth generation b '-quark at LEP-II at root s=196-209GeV
- 2007
-
In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 50:3, s. 507-518
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Journal article (peer-reviewed)abstract
- A search for the pair production of fourth generation b'-quarks was performed using data taken by the DELPHI detector at LEP-II. The analysed data were collected at centre-of-mass energies ranging from 196 to 209 GeV, corresponding to an integrated luminosity of 420 pb(-1). No evidence for a signal was found. Upper limits on BR(b'-> bZ) and BR(b'-> bZ) were obtained for b' masses ranging from 96 to 103 GeV/c(2) stop. These limits, together with the theoretical branching ratios predicted by a sequential four generations model, were used to constrain the value of R-CKM=vertical bar V-cb(') /V-tb'V-tb vertical bar there V-cb', V-tb' and V-tb are elements of the extended CKM matrix.
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| 22. |
- Abdallah, J., et al.
(author)
-
Search for pentaquarks in the hadronic decays of the Z boson with the DELPHI detector at LEP
- 2007
-
In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 653:2-4, s. 151-160
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Journal article (peer-reviewed)abstract
- The quark model does not exclude states composed of more than three quarks, like pentaquark systems. Controversial evidence for such states has been published in the last years, in particular: for a strange pentaquark Theta(1540)(+); for a double-strange state, the Xi(1862)(--), subsequently called Phi(1860)--; and for a charmed state, the Theta(c)(3100)(0). If confirmed, a full pentaquark family might exist; such pentaquark states could be produced in e(+)e(-) annihilations near the Z energy. In this Letter a search for pentaquarks is described using the DELPHI detector at LEP, characterized by powerful particle identification sub-systems crucial in the separation of the signal from the background for these states. At 95% CL, upper limits are set on the production rates N of such particles and their charge-conjugate state per Z decay: N-Theta+ x Br(Theta(+) -> pK(S)(0)) < 5.1 x 10(-4), N Theta++ < 1.6 x 10(-3), N Phi(1860)-- x Br((P(1860)-- -> Xi(-)pi(-)) < 2.9 x 10(-4), N-Theta c(3100)0 x Br(Theta(c)(3100)(0) -> D*(+)p) < 8.8 x 10(-4).
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| 23. |
- Abdallah, J., et al.
(author)
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Study of b-quark mass effects in multijet topologies with the DELPHI detector at LEP
- 2008
-
In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; C:55, s. 525-538
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Journal article (peer-reviewed)abstract
- The effect of the heavy b-quarkmass on the two, three and four-jet rates is studied using LEP data collected by the DELPHI experiment at the Z peak in 1994 and 1995. The rates of b-quark jets and light quark jets (l = uds) in events with n = 2, 3, and 4 jets, together with the ratio of two and four-jet rates of b-quarks with respect to light-quarks, R-n(bl), have been measured with a double-tag technique using the CAMBRIDGE jet-clustering algorithm. A comparison between experimental results and theory (matrix element or Monte Carlo event generators such as PYTHIA, HERWIG andARIADNE) is done after the hadronisation phase. Using the four-jet observabl R-4(bl), a measurement of the b-quark mass using massive leading-order calculations gives: m(b)(M-Z) = 3.76 +/- 0.32 (stat) +/- 0.17 (syst) +/- 0.22 (had) +/- 0.90 (theo) GeV/c(2). This result is compatible with previous three-jet determinations at the M-Z energy scale and with low energy mass measurements evolved to the M-Z scale using QCD renormalisation group equations.
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| 24. |
- Abdallah, J., et al.
(author)
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Study of W-boson polarisations and triple gauge boson couplings in the reaction e(+)e(-)-> W+W- at LEP 2
- 2008
-
In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; C:54, s. 345-364
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Journal article (peer-reviewed)abstract
- A determination of the single W spin density matrix (SDM) elements in the reaction e(+)e(-) -> W+W--> l nu q (q) over bar (l=e/mu) is reported at centre-of-mass energies between 189 and 209GeV. The data sample used corresponds to an integrated luminosity of 520pb(-1) taken by DELPHI between 1998 and 2000. The single W SDM elements, rho(W +/-)(tau tau') (tau,tau'=+/- 1 or 0), are determined as a function of the W- production angle with respect to the e(-) beam direction and are obtained from measurements of the W decay products by the application of suitable projection operators, Lambda(tau tau'), which assume the V-A coupling of the W-boson to fermions. The measured SDM elements are used to obtain the fraction of longitudinally polarised Ws, with the result: sigma(L)/sigma(tot) = 24.9 +/- 4.5 (stat) +/- 2.2 (syst)% at a mean energy of 198 GeV. The SDM elements are also used to determine the triple gauge couplings Delta g(1)(Z), Delta kappa(gamma), lambda(gamma) and g(4)(Z), (kappa) over tilde (Z) and (lambda) over tilde (Z). For the CP-violating couplings the results of single parameter fits are: g(4)(Z) = -0.39(-0.20)(+0.19) (kappa) over tilde (Z) = -0.09(-0.05)(+0.08) (lambda) over tilde (Z) = -0.08 +/- 0.07. The errors are a combination of statistical and systematic errors. All results are consistent with the Standard Model.
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| 25. |
- Abdallah, J., et al.
(author)
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Z gamma* production in e(+) e(-) interactions at root s=183-209 GeV
- 2007
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In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 51:3, s. 503-523
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Journal article (peer-reviewed)abstract
- Measurements of Z gamma* production are presented using data collected by the DELPHI detector at centre-of-mass energies ranging from 183 to 209 GeV, corresponding to an integrated luminosity of about 667 pb(-1). The measurements cover a wide range of the possible final state four-fermion configurations: hadronic and leptonic (e(+) e(-) q (q) over bar, mu(+) mu(-) q (q) over bar ,q (q) over barv (v) over bar), fully leptonic (l(+) l(-) l' (+) l'(-)) and fully hadronic. nal states (q (q) over barq (q) over bar, with a low mass q (q$) over bar pair). Measurements of the Z gamma* cross-section for the various. nal states have been compared with the Standard Model expectations and found to be consistent within the errors. In addition, a total cross-section measurement of the l(+) l(-) l'(+)l'(-) cross-section is reported, and found to be in agreement with the prediction of the Standard Model.
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