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41.
  • Abdallah, J., et al. (författare)
  • Single intermediate vector boson production in e(+)e(-) collisions at root s=183-209 GeV
  • 2006
  • Ingår i: European Physical Journal C. Particles and Fields. - : Springer. - 1434-6044 .- 1434-6052. ; 45:2, s. 273-289
  • Tidskriftsartikel (refereegranskat)abstract
    • The production of single charged and neutral intermediate vector bosons in e(+)e(-) collisions has been studied in the data collected by the DELPHI experiment at LEP at centre-of-mass energies between 183 and 209 GeV, corresponding to an integrated luminosity of about 640 pb(-1). The measured cross-sections for the reactions, determined in limited kinematic regions, are in agreement with the Standard Model predictions.
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42.
  • Abdallah, J, et al. (författare)
  • The measurement of alpha(8) from event shapes with the DELPHI detector at the highest LEP energies
  • 2004
  • Ingår i: European Physical Journal C. Particles and Fields. - : Springer. - 1434-6044. ; 37:1, s. 1-23
  • Tidskriftsartikel (refereegranskat)abstract
    • Hadronic event shape distributions are determined from data in e(+)e(-) collisions between 183 and 207 GeV. From these the strong coupling alpha(s) is extracted in O(alpha(s)(2)), NLLA and matched O(alpha(s)(2))+ NLLA theory. Hadronisation corrections evaluated with fragmentation model generators as well as an analytical power ansatz are applied. Comparing these measurements to those obtained at and around M-Z allows a combined measurement of alpha(s) from all DELPHI data and a test of the energy dependence of the strong coupling.
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43.
  • Abdallah, J, et al. (författare)
  • A study of the energy evolution of event shape distributions and their means with the DELPHI detector at LEP
  • 2003
  • Ingår i: European Physical Journal C. Particles and Fields. - : Springer. - 1434-6044. ; 29:3, s. 285-312
  • Tidskriftsartikel (refereegranskat)abstract
    • Infrared and collinear safe event shape distributions and their mean values are determined in e(+)e(-) collisions at centre-of-mass energies between 45 and 202GeV. A phenomenological analysis based on power correction models including hadron mass effects for both differential distributions and mean values is presented. Using power corrections, alpha(s) is extracted from the mean values and shapes. In an alternative approach, renormalisation group invariance (RGI) is used as an explicit constraint, leading to a consistent description of mean values without the need for sizeable power corrections. The QCD beta-function is precisely measured using this approach. From the DELPHI data on Thrust, including data from low energy experiments, one finds beta(0) = 7.86 +/- 0.32 for the one loop coefficient of the beta-function or, assuming QCD, n(f) = 4.75 +/- 0.44 for the number of active flavours. These values agree well with the QCD expectation of beta(0) = 7.67 and n(f) 5. A direct measurement of the full logarithmic energy slope excludes light gluinos with a mass below 5GeV.
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44.
  • Abdallah, J, et al. (författare)
  • Bose-Einstein correlations in W+W- events at LEP2
  • 2005
  • Ingår i: European Physical Journal C. Particles and Fields. - : Springer. - 1434-6044. ; 44:2, s. 161-174
  • Tidskriftsartikel (refereegranskat)abstract
    • Bose-Einstein correlations (BEC) between final state particles in the reaction e(+)e(-) -> W+ W- -> q(1)(q(2)) over barq(3)(q(4)over bar>) over bar) have been studied. Data corresponding to a total integrated luminosity of 550 pb(-1), recorded by the DELPHI detector at centre-of-mass energies ranging from 189 to 209 GeV, were analysed. An indication for inter-W BEC between like-sign particles has been found at the level of 2.4 standard deviations of the combined statistical and systematic uncertainties.
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45.
  • Abdallah, J, et al. (författare)
  • Charged particle multiplicity in three-jet events and two-gluon systems
  • 2005
  • Ingår i: European Physical Journal C. Particles and Fields. - : Springer. - 1434-6044. ; C:44, s. 311-331
  • Tidskriftsartikel (refereegranskat)abstract
    • The charged particle multiplicity in hadronic three-jet events from Z decays is investigated. The topology dependence of the event multiplicity is found to be well described by a modified leading logarithmic prediction. A parameter fit of the prediction to the data yields a measurement of the colour factor ratio C-A/C-F with the result C-A/C-F = 2.261 +/- 0.014(stat). +/- 0.036(exp). +/- 0-066(theo). in agreement with the SU(3) expectation of QCD. The quark-related contribution to the event multiplicity is subtracted from the three-jet event multiplicity resulting in a measurement of the multiplicity of two-gluon colour-singlet states over a wide energy range. The ratios r = N-gg(s)/Ng (g) over bar (s) of the gluon and quark multiplicities and r((1)) = N'(gg)(s)/N'g (g) over bar (s) of their derivatives are compared with perturbative calculations. While a good agreement between calculations and data is observed for r((1)), larger deviations are found for r indicating that non-perturbative effects are more important for r than for r((1)).
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46.
  • Abdallah, J, et al. (författare)
  • Coherent soft particle production in Z decays into three jets
  • 2005
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier. - 0370-2693. ; 605:1-2, s. 37-48
  • Tidskriftsartikel (refereegranskat)abstract
    • Low-energy particle production perpendicular to the event plane in three-jet events produced in Z decays in e(+)e(-) annihilation is measured and compared to that perpendicular to the event axis in two-jet events. The topology dependence of the hadron production ratio is found to agree with a leading-order QCD prediction. This agreement and especially the need for the presence of a destructive interference term gives evidence for the coherent nature of gluon radiation. Hadron production in three-jet events is found to be directly proportional to a single topological scale function of the inter-jet angles. The slope of the dependence of the multiplicity with respect to the topological scale was measured to be 2.211 +/- 0.014(stat.) +/- 0.053(syst.) in good agreement with the expectation given by the colour-factor ratio C-A/C-F = 9/4. This result strongly supports the assumption of local parton-hadron duality, LPHD, at low hadron momentum.
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47.
  • Abdallah, J, et al. (författare)
  • Final results from DELPHI on the searches for SM and MSSM neutral Higgs bosons
  • 2004
  • Ingår i: European Physical Journal C. Particles and Fields. - : Springer. - 1434-6044. ; 32:2, s. 145-183
  • Tidskriftsartikel (refereegranskat)abstract
    • These final results from DELPHI searches for the Standard Model (SM) Higgs boson, together with benchmark scans of the Minimal Supersymmetric Standard Model (MSSM) neutral Higgs bosons, used data taken at centre-of-mass energies between 200 and 209 GeV with a total integrated luminosity of 224 pb(-1). The data from 192 to 202 GeV are reanalysed with improved b-tagging for MSSM final states decaying to four b-quarks. The 95% confidence level lower mass bound on the Standard Model Higgs boson is 114.1 GeV/c(2). Limits are also given on the lightest scalar and pseudo-scalar Higgs bosons of the MSSM.
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48.
  • Abdallah, J, et al. (författare)
  • Measurement of inclusive f(1) (1285) and f(1) (1420) production in Z decays with the DELPHI detector
  • 2003
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier. - 0370-2693. ; 569:3-4, s. 129-139
  • Tidskriftsartikel (refereegranskat)abstract
    • DELPHI results are presented on the inclusive production of two (K(K) over bar π)(0) states in the mass region 1.2-1.6 GeV/c(2) in hadronic Z decays at LEP I. The measured masses (widths) are 1274 +/- 6 MeV/c(2) (29 +/- 12 MeV/c(2)) and 1426 +/- 6 MeV/c(2) (51 +/- 14 MeV/c(2)), respectively. A partial-wave analysis of the (K(K) over bar π)(0) system shows that the first peak is consistent with the I-G (J(PC)) = 0(+)(1(++))/(0(-+))a(0)(980)pi and the second with the I-G (J(PC)) = 0(+)(1(++))K*(892)(K) over bar + c.c. assignments. The total hadronic production rates per hadronic Z decay are (0.165 +/- 0.051) and (0.056 +/- 0.012), respectively. These measurements are consistent with the two states being the f(1) (1285) and f(1) (1420) mesons. (C) 2003 Published by Elsevier B.V.
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49.
  • Abdallah, J, et al. (författare)
  • Measurement of the e(+)e(-)-> W+W- gamma cross-section and limits on anomalous quartic gauge couplings with DELPHI
  • 2003
  • Ingår i: European Physical Journal C. Particles and Fields. - : Springer. - 1434-6044. ; 31:2, s. 139-147
  • Tidskriftsartikel (refereegranskat)abstract
    • W(+)W(-)gamma production at LEP2 is studied using data collected with the DELPHI detector at centre-of-mass energies between 189 GeV and 209 GeV, corresponding to an integrated luminosity of about 600 pb(-1). Cross-sections are measured for the production of W+W- with a hard, central and isolated photon in the final state, and are found to be compatible with the Standard Model prediction. The photon energy spectra are used to derive limits on anomalous contributions to the W(+)W(-)Z(o)gamma and W(+)W(-)gammagamma vertices.
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50.
  • Abdallah, J, et al. (författare)
  • Measurement of the Lambda(0)(b) decay form factor
  • 2004
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier. - 0370-2693. ; 585:1-2, s. 63-84
  • Tidskriftsartikel (refereegranskat)abstract
    • The form factor of A(o)(b) baryons is estimated using 3.46 x 10(6) hadronic Z decays collected by the DELPM experiment between 1992 and 1995. Charmed A(c)(+) baryons fully reconstructed in the pK(-)pi(+), pK(o)(s), and Api(+)pi(+)pi(-) modes, are associated to a c S lepton with opposite charge in order to select A(o)(b) --> A(c)(+)l(-)v(l) decays. From a combined likelihood and event rate fit to the b C distribution of the Isgur-Wise variable w, and using the Heavy Quark Effective Theory (HQET), the slope of the b-baryon form factor is measured to be p(2)=2.03+/-0.46(stat)(-1.00)(+0.72)(syst). The exclusive semileptonic branching fraction Br(A(b)(o) --> A(c)(+)l(-)v(l)) can be derived from p(2) and is found to be (5.0(-0.8)(+1.1)(stat)(-1.2)(+1.6) (syst))%. Limits on other branching fractions are also obtained. (C) 2004 Published by Elsevier B.V.
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