11. |
- Abdallah, J, et al.
(author)
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Search for B-s(0)-(B-s(0))over-bar oscillations in DELPHI using high-p(t) leptons
- 2004
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In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 35:1, s. 35-52
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Journal article (peer-reviewed)abstract
- Oscillations in the B-s(0)- <(B-s(0))over bar> system were studied in events selected from about 4.3 million hadronic Z(0) decays registered by DELPHI between 1992 and 2000. This paper presents updates of two published analyses ([11, 12]). The first analysis, which utilizes leptons emitted with large momentum transverse to a jet, was improved by means of a better algorithm for the vertex reconstuction and a new algorithm for flavour-tagging at production time. The second analysis, which utilizes D-s-lepton events, was improved by optimizing the treatment of proper time resolution. No signal of B-s(0) oscillations was observed and limits on the mass difference between the physical B-s(0) states were obtained to be: Deltam(s)>8.0 ps-1 at the 95% C.L. with a sensitivity of Deltam(s)= 9.1 ps(-1) in the high p(t) lepton analysis and Deltam(s)>4.9 ps(-1) at the 95% C.L. with a sensitivity of Deltam(s)=8.6 ps(-1) in the D-s-lepton analysis. Previously published results on these analyses are superseded. The combination of these results with those obtained in other independent analyses previously performed in DELPHI (D-s-hadron, exclusive B-s(0), inclusive vertex) gives: Deltam(s)>8.5 ps(-1) at the 95% C.L. with a sensitivity of Deltam(s)=12.0 ps(-1).
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12. |
- Abdallah, J, et al.
(author)
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Search for fermiophobic Higgs bosons in final states with photons at LEP 2
- 2004
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In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 35:3, s. 313-324
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Journal article (peer-reviewed)abstract
- Higgs boson production with subsequent decay to photons was searched for in the data collected by the DELPHI detector at centre-of-mass energies between 183 GeV and 209 GeV, corresponding to a total integrated luminosity of nearly 650 pb(-1). No evidence for a signal was found, and limits were set on h(0)Z(0) and h(0)A(0) production with h(0) decay to photons. These results were used to exclude regions in the parameter space of fermiophobic scenarios of Two Higgs Doublet Models.
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13. |
- Abdallah, J, et al.
(author)
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Search for supersymmetric particles assuming R-parity non-conservation in e(+)e(-) collisions at root s=192 to 208 GeV
- 2004
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In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 36:1, s. 1-23
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Journal article (peer-reviewed)abstract
- Searches for pair-production of supersymmetric particles under the assumption of non-conservation of R-parity with a dominant LL (E) over bar or (U) over bar(D) over bar(D) over bar term have been performed using the data collected by the DELPHI experiment at LEP in e(+)e(-) collisions at centre-of-mass energies from 192 up to 208 GeV. No excess of data above Standard Model expectations was observed. The results were used to constrain the MSSM parameter space and to derive limits on the masses of supersymmetric particles.
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14. |
- Abdallah, J, et al.
(author)
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Search for SUSY in the AMSB scenario with the DELPHI detector
- 2004
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In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 34:2, s. 145-156
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Journal article (peer-reviewed)abstract
- The DELPHI experiment at the LEP e (+) e(-) collider collected almost 700 pb(-1) at centre-of-mass energies above the Z(0) mass pole and up to 208 GeV. Those data were used to search for SUSY in the Anomaly Mediated SUSY Breaking (AMSB) scenario with a flavour independent common sfermion mass parameter. The searches covered several possible signatures experimentally accessible at LEP, with either the neutralino, the sneutrino or the stau being the Lightest Supersymmetric Particle (LSP). They included: the search for nearly mass-degenerate chargino and neutralino, which is a typical feature of AMSB; the search for Standard-Model-like or invisibly decaying Higgs boson; the search for stable staus; the search for cascade decays of SUSY particles resulting in the LSP and a low multiplicity final state containing neutrinos. No evidence of a signal was found, and thus constraints were set in the space of the parameters of the model.
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15. |
- Abdallah, J, et al.
(author)
-
Study of tau-pair production in photon-photon collisions at LEP and limits on the anomalous electromagnetic moments of the tau lepton
- 2004
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In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 35:2, s. 159-170
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Journal article (peer-reviewed)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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16. |
- Abdallah, J, et al.
(author)
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The measurement of alpha(8) from event shapes with the DELPHI detector at the highest LEP energies
- 2004
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In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 37:1, s. 1-23
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Journal article (peer-reviewed)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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17. |
- Abdallah, J, et al.
(author)
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A study of the energy evolution of event shape distributions and their means with the DELPHI detector at LEP
- 2003
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In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 29:3, s. 285-312
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Journal article (peer-reviewed)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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18. |
- Abdallah, J, et al.
(author)
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Final results from DELPHI on the searches for SM and MSSM neutral Higgs bosons
- 2004
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In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 32:2, s. 145-183
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Journal article (peer-reviewed)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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19. |
- Abdallah, J, et al.
(author)
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Inclusive b decays to wrong sign charmed mesons
- 2003
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In: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 561:1-2, s. 26-40
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Journal article (peer-reviewed)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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20. |
- Abdallah, J, et al.
(author)
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Measurement of the e(+)e(-)-> W+W- gamma cross-section and limits on anomalous quartic gauge couplings with DELPHI
- 2003
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In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 31:2, s. 139-147
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Journal article (peer-reviewed)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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