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Träfflista för sökning "WFRF:(Gazis E.) srt2:(2002-2004)"

Sökning: WFRF:(Gazis E.) > (2002-2004)

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1.
  • Abdallah, J, et al. (författare)
  • Search for doubly charged Higgs bosons at LEP2
  • 2003
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - Elsevier. - 0370-2693. ; 552:3-4, s. 127-137
  • Tidskriftsartikel (refereegranskat)abstract
    • A search for pair-produced doubly charged Higgs bosons has been performed using the data collected by the DELPHI detector at LEP at centre-of-mass energies between 189 and 209 GeV. No excess is observed in the data with respect to the Standard Model background. A lower limit for the mass of 97.3 GeV/c(2) at the 95% confidence level has been set for doubly charged Higgs bosons in left-right symmetric models for any value of the Yukawa coupling between the Higgs bosons and the tau leptons. (C) 2002 Published by Elsevier Science B.V.
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2.
  • Abdallah, J, et al. (författare)
  • Search for single top production via FCNC at LEP at root s=189-208 GeV
  • 2004
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - Elsevier. - 0370-2693. ; 590:1-2, s. 21-34
  • Tidskriftsartikel (refereegranskat)abstract
    • A search for single top production (e(+)e(-) --> t (c) over bar) via flavour changing neutral currents (FCNC) was performed using the data taken by the DELPHI detector at LEP2. The data analyzed have been accumulated at center-of-mass energies ranging from 189 to 208 GeV. Limits at 95% confidence level were obtained on the anomalous coupling parameters kappa(gamma) and kappa(Z). (C) 2004 Published by Elsevier B.V.
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3.
  • Abdallah, J, et al. (författare)
  • A precise measurement of the B+, B-0 and mean b-hadron lifetime with the DELPHI detector at LEP I
  • 2004
  • Ingår i: European Physical Journal C. Particles and Fields. - Springer. - 1434-6044. ; 33:3, s. 307-324
  • Tidskriftsartikel (refereegranskat)abstract
    • Final results from the DELPHI Collaboration on the lifetime of B+ and B-0 mesons and the mean b-hadron lifetime, are presented using the data collected at the Z(0) peak in 1994 and 1995. Elaborate, inclusive, secondary vertexing methods have been employed to ensure a b-hadron reconstruction with good efficiency. To separate samples of B+ and B-0 mesons, high performance neural network techniques are used that achieve very high purity signals. The results obtained are: tau(B+) = 1.624+/-0.014 (stat)+/-0.018 (syst) ps tau(B)0 = 1.531+/-0.021 (stat)+/-0.031 (syst) ps tau(B+)/tau(B)0 = 1.060+/-0.021 (stat)+/-0.024 (syst) and for the average b-hadron lifetime: taub/tau(B)0 = 1.570+/-0.005 (stat)+/-0.008 (syst) ps.
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4.
  • Abdallah, J, et al. (författare)
  • Inclusive b decays to wrong sign charmed mesons
  • 2003
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - Elsevier. - 0370-2693. ; 561:1-2, s. 26-40
  • Tidskriftsartikel (refereegranskat)abstract
    • The production of wrong sign charmed mesons b --> (D) over bar X-(s), D-(s) = (D-0, D+, D-s), is studied using the data collected by the DELPHI experiment in the years 1994 and 1995. Charmed mesons in Z --> b (b) over bar events are exclusively reconstructed by searching for the decays D-0 --> K(-)pi(+), D+ --> K(-)pi(+)pi(+) and D-s(+) --> phipi(+) --> K(+)K(-)pi(+). The wrong sign contribution is extracted by using two discriminant variables: the charge of the b-quark at decay time, estimated from the charges of identified particles, and the momentum of the charmed meson in the rest frame of the b-hadron. The inclusive branching fractions of b-hadrons into wrong sign charm mesons are measured to be: B(b --> (D) over bar X-0) + B(b --> D-X) = (9.3 +/- 1.7(stat) +/- 1.3(syst) +/- 0.4(B))%, B(b --> Ds-X) = (10.1 +/- 1.0(stat) +/- 0.6(syst) +/- 2.8(B))% where the first error is statistical, the second and third errors are systematic. (C) 2003 Published by Elsevier Science B.V.
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5.
  • Abdallah, J, et al. (författare)
  • Study of tau-pair production in photon-photon collisions at LEP and limits on the anomalous electromagnetic moments of the tau lepton
  • 2004
  • Ingår i: European Physical Journal C. Particles and Fields. - Springer. - 1434-6044. ; 35:2, s. 159-170
  • Tidskriftsartikel (refereegranskat)abstract
    • Tau-pair production in the process e(+)e(-) --> e(+)e(-) tau(+)tau(-) was studied using data collected by the DELPHI experiment at LEP2 during the years 1997 - 2000. The corresponding integrated luminosity is 650 pb(-1). The values of the cross-section obtained are found to be in agreement with QED predictions. Limits on the anomalous magnetic and electric dipole moments of the tau lepton are deduced.
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6.
  • Abdallah, J, et al. (författare)
  • A measurement of the branching fractions of the b-quark into charged and neutral b-hadrons
  • 2003
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - Elsevier. - 0370-2693. ; 576:1-2, s. 29-42
  • Tidskriftsartikel (refereegranskat)abstract
    • The production fractions of charged and neutral b-hadrons in b-quark events from Z(0) decays have been measured with the DELPHI detector at LEP. An algorithm has been developed, based on a neural network, to estimate the charge of the weakly-decaying b-hadron by distinguishing its decay products from particles produced at the primary vertex. From the data taken in the years 1994 and 1995, the fraction of (b) over bar -quarks fragmenting into positively charged weakly-decaying b-hadrons has been measured to be: f(+) = (42.09+/-0.82(stat)+/-0.89(syst))%. Subtracting the rates for charged Xi(b)(+) and Omega(b)(+) baryons gives the production fraction of B+ mesons: f(Bu) = (40.99+/-0.82(stat)+/-1.11 (syst)) %.
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7.
  • Abdallah, J, et al. (författare)
  • A precise measurement of the tau lifetime
  • 2004
  • Ingår i: European Physical Journal C. Particles and Fields. - Springer. - 1434-6044. ; 36:3, s. 283-296
  • Tidskriftsartikel (refereegranskat)abstract
    • The tau lepton lifetime has been measured with the e(+) e(-) --> tau(+) tau(-) events collected by the DELPHI detector at LEP in the years 1991 - 1995. Three different methods have been exploited, using both one-prong and three-prong tau decay channels. Two measurements have been made using events in which both taus decay to a single charged particle. Combining these measurements gave tau(tau) ( 1 prong) = 291.8 +/- 2.3(stat) +/- 1.5(sys) fs. A third measurement using taus which decayed to three charged particles yielded tau(tau) (3 prong) = 288.6 +/- 2.4(stat) +/- 1.3(sys) fs. These were combined with previous DELPHI results to measure the tau lifetime, using the full LEP1 data sample, to be tau(tau) = 290.9 +/- 1.4(stat) +/- 1.0(sys) fs.
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8.
  • Abdallah, J, et al. (författare)
  • Determination of the e(+)e(-)->gamma gamma(gamma) cross-section at LEP 2
  • 2004
  • Ingår i: European Physical Journal C. Particles and Fields. - Springer. - 1434-6044. ; 37:4, s. 405-419
  • Tidskriftsartikel (refereegranskat)abstract
    • A test of the benchmark QED process e(+) e(-) -->gammagamma(gamma) is reported, using the data collected with the DELPHI detector at LEP 2. The data analysed were recorded at centre-of-mass energies ranging from 161 GeV to 208 GeV and correspond to a total integrated luminosity of 656.4 pb(-1). The Born cross-section for the process e(+) e(-)-->gammagamma(gamma) was determined, confirming the validity of QED at the highest energies ever attained in electron-positron collisions. Lower limits on the parameters of a number of possible deviations from QED, predicted within theoretical frameworks expressing physics beyond the Standard Model, were derived.
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9.
  • 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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10.
  • Abdallah, J, et al. (författare)
  • Measurement of the forward-backward asymmetries of e(+)e(-)-> Z -> b(b)over-bar and e(+)e(-)-> Z -> c(c)over-bar using prompt leptons
  • 2004
  • Ingår i: European Physical Journal C. Particles and Fields. - Springer. - 1434-6044. ; 34:2, s. 109-125
  • Tidskriftsartikel (refereegranskat)abstract
    • The forward-backward asymmetries of the processes e(+) e(-) --> Z --> b (b) over bar and e(+)e(-) --> Z --> c (c) over bar were measured from a sample of hadronic Z decays collected by the DELPHI experiment between 1993 and 1995. Enriched samples of b (b) over bar and c (c) over bar events were obtained using lifetime information. The tagging of b and c quarks in these samples was based on the semileptonic decay channels b/c --> X + mu and b/c --> X + e combined with charge flow information from the hemisphere opposite to the lepton. Combining the A(FB)(b (b) over bar) and A(FB)(c (c) over bar) measurements presented in this paper with published results based on 1991 and 1992 DELPHI data samples, the following pole asymmetries were obtained: A(FB)(0,b) = 0.1021 +/- 0.0052 (stat) +/- 0.0024 (syst) A(FB)(0,c) = 0.0728 +/- 0.0086 (stat) +/- 0.0063 (syst) The effective value of the weak mixing angle derived from these measurements is sin(2) theta(W,eff)(lept) = 0.23170 +/- 0.00097.
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