| 1. |
- Abreu, P., et al.
(författare)
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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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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 13:4, s. 573-589
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Abreu, P., et al.
(författare)
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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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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 19:1, s. 15-28
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Tidskriftsartikel (refereegranskat)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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| 3. |
- Abreu, P., et al.
(författare)
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Search for sleptons in e+e- collisions at √s = 183 to 189 GeV
- 2001
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 19:1, s. 29-42
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Tidskriftsartikel (refereegranskat)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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| 4. |
- Abreu, P, et al.
(författare)
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b-tagging in DELPHI at LEP
- 2004
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 32:2, s. 185-208
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Tidskriftsartikel (refereegranskat)abstract
- The standard method used for tagging b-hadrons in the DELPHI experiment at the CERN LEP Collider is discussed in detail. The main ingredient of b-tagging is the impact parameters of tracks, which relies mostly on the vertex detector. Additional information, such as the mass of particles associated to a secondary vertex, significantly improves the selection efficiency and the background suppression. The paper describes various discriminating variables used for the tagging and the procedure of their combination. In addition, applications of b-tagging to some physics analyses, which depend crucially on the performance and reliability of b-tagging, are described briefly.
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| 5. |
- Abreu, P, et al.
(författare)
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Measurement of the inclusive charmless and double-charm B branching ratios
- 1998
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Ingår i: PHYSICS LETTERS B. - : ELSEVIER SCIENCE BV. - 0370-2693. ; 426:1-2, s. 193-206
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The DELPHI experiment at LEP has measured the inclusive charmless B hadron decay branching ratio, the B branching ratio into two charmed particles, and the total number of charmed particles per B decay, using the hadronic Z data taken between 1992 and 199
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| 6. |
- Abreu, P, et al.
(författare)
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A search for eta '(c) production in photon-photon fusion at LEP
- 1998
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Ingår i: PHYSICS LETTERS B. - : ELSEVIER SCIENCE BV. - 0370-2693. ; 441:1-4, s. 479-490
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A search for the production of the eta(c)' meson, the first radial excitation of the ground state of charmonium eta(c)(2980), in the photon-photon fusion reaction at LEP has been performed using the data collected by the DELPHI detector during 1992-1996.
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| 7. |
- Abreu, P, et al.
(författare)
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A study of the hadronic resonance structure in the decay tau -> 3 pi nu(tau)
- 1998
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Ingår i: PHYSICS LETTERS B. - : ELSEVIER SCIENCE BV. - 0370-2693. ; 426:3-4, s. 411-427
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The hadronic structure of the decay of the tau lepton to three charged particles, tau --> 3 pi nu(tau), is studied using data collected by the DELPHI detector at LEP between 1992 and 1995. The invariant mass of the 3 pi system, m(3 pi), is fitted using th
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| 8. |
- Abreu, P, et al.
(författare)
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Cross-sections and leptonic forward-backward asymmetries from the Z(0) running of LEP
- 2000
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Ingår i: EUROPEAN PHYSICAL JOURNAL C. - : SPRINGER-VERLAG. - 1434-6044. ; 16:3, s. 371-405
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Tidskriftsartikel (refereegranskat)abstract
- During 1993 and 1995 LEP was run at 3 energies near the Z(0) peak in order to give improved measurements of the mass and width of the resonance. During 1994, LEP operated only at the Z(0) peak. In total DELPHI accumulated data corresponding to an integrat
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| 9. |
- Abreu, P, et al.
(författare)
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First evidence for a charm radial excitation, D-*'
- 1998
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Ingår i: PHYSICS LETTERS B. - : ELSEVIER SCIENCE BV. - 0370-2693. ; 426:1-2, s. 231-242
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Using D*+ mesons exclusively reconstructed in the DELPHI detector at LEP, an excess of 66 +/- 14(stat.) events is observed in the D(*+)pi(+)pi(-) final state with a mass of 2637 +/- 2(stat.) +/- 6(syst.) MeV/c(2) and a full width smaller than 15 MeV/c(2)
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| 10. |
- Abreu, P, et al.
(författare)
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Investigation of the splitting of quark and gluon jets
- 1998
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Ingår i: EUROPEAN PHYSICAL JOURNAL C. - : SPRINGER VERLAG. - 1434-6044. ; 4:1, s. 1-17
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The splitting processes in identified quark and gluon jets are investigated using longitudinal and transverse observables. The jets are selected from symmetric three-jet events measured in Z decays with the DELPHI detector in 1991-1994. Gluon jets are ide
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