| 41. |
- Abdallah, J, et al.
(författare)
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Measurement of the Lambda(0)(b) decay form factor
- 2004
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 585:1-2, s. 63-84
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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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| 42. |
- Abdallah, J., et al.
(författare)
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Measurement of the mass and width of the W boson in e(+) e(-) collisions at root s=161-209 GeV
- 2008
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; C:55, s. 1-38
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Tidskriftsartikel (refereegranskat)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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| 43. |
- Abdallah, J., et al.
(författare)
-
Measurement of the tau lepton polarisation at LEP2
- 2008
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Ingår i: 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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Tidskriftsartikel (refereegranskat)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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| 44. |
- Abdallah, J, et al.
(författare)
-
Measurement of the W-pair production cross-section and W branching ratios in e(+)e(-) collisions at root s=161-209 GeV
- 2004
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 34:2, s. 127-144
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Tidskriftsartikel (refereegranskat)abstract
- These final results on e(+) e(-) W+ W- production cross-section measurements at LEP2 use data collected by the DELPHI detector at centre-of-mass energies up to 209 GeV. Measurements of total cross-sections, W angular differential distributions and decay branching fractions, and the value of the CKM element |V-cs| are compared to the expectations of the Standard Model. These results supersede all values previously published by DELPHI.
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| 45. |
- Abdallah, J, et al.
(författare)
-
Measurement of vertical bar Vcb vertical bar using the semileptonic decay (B)d(0))over-bar -> D*+l(-)(nu)over-barl
- 2004
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 33:2, s. 213-232
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Tidskriftsartikel (refereegranskat)abstract
- Data from Z decays in DELPHI have been searched for <(B-d(o))over bar> --> D*+ l(-) (ν) over bar (l) with the D*+ decaying to D(0)pi(+) and D-0 --> K(-)pi(+), K(-)pi(+)pi(+)pi(-) or K- pi(+)(pi(0)). These events are used to measure the CKM matrix element V-cb and the form factor slope, rho(A1)(2): F-D*(1) V-cb = 0.0392 +/- 0.0018 +/- 0.0023; rho(A1)(2) = 1.32 +/- 0.15 +/- 0.33 corresponding to a branching fraction: BR(<(B-d(0))over bar> --> D(*+)l(-)(ν) over bar (l)) = (5.90 +/- 0.22 +/- 0.50)%. Combining these and previous DELPHI measurements gives: FD*(1)V-cb = 0.0377 +/- 0.0011 +/- 0.0019, rho(A1)(2) = 1.39 +/- 0.10 +/- 0.33 and BR(<(B-d(0))over bar> --> D(*+)l(-)(ν) over bar (l)) = (5.39 +/- 0.11 +/- 0.34)% Using F-D*(1) = 0.91 +/- 0.04, yields: V-cb = 0.0414 +/- 0.0012(stat.) +/- 0.0021(syst.) +/- 0.0018 (theory). The b-quark semileptonic branching fraction into a D*+ emitted from higher mass charmed excited states has also been measured to be: BR(b --> D*+ Xl(-)(ν) over bar (l)) = (0.67 +/- 0.08 +/- 0.10)%.
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| 46. |
- Abdallah, J, et al.
(författare)
-
Observation of the muon inner bremsstrahlung at LEP1
- 2008
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; C:57, s. 499-514
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Tidskriftsartikel (refereegranskat)abstract
- Muon bremsstrahlung photons converted in front of the DELPHI main tracker (TPC) in dimuon events at LEP1 were studied in two photon kinematic ranges: 0.2< E-gamma <= 1 GeV and transverse momentum with respect to the parent muon p(T) < 40 MeV/c, and 1< E-gamma <= 10 GeV and pT < 80 MeV/c. A good agreement of the observed photon rate with predictions from QED for the muon inner bremsstrahlung was found, contrary to the anomalous soft photon excess that has been observed recently in hadronic Z(0) decays. The obtained ratios of the observed signal to the predicted level of the muon bremsstrahlung are 1.06 +/- 0.12 +/- 0.07 in the photon energy range 0.2< E-gamma <= 1 GeV and 1.04 +/- 0.09 +/- 0.12 in the photon energy range 1< E-gamma <= 10 GeV. The bremsstrahlung dead cone is observed for the first time in the direct photon production at LEP.
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| 47. |
- Abdallah, J, et al.
(författare)
-
Photon events with missing energy in e(+)e(-) collisions at root s=130 to 209 GeV
- 2005
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 38:4, s. 395-411
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Tidskriftsartikel (refereegranskat)abstract
- The production of single- and multi-photon events has been studied in the reaction e(+) e(-) --> gamma(gamma) + invisible particles. The data collected with the DELPHI detector during the years 1999 and 2000 at centre-of-mass energies between 191 GeV and 209 GeV was combined with earlier data to search for phenomena beyond the Standard Model. The measured number of light neutrino families was consistent with three and the absence of an excess of events beyond that predicted by the Standard Model processes was used to set limits on new physics. Both model-independent searches and searches for new processes predicted by supersymmetric and extra-dimensional models have been made. Limits on new non-standard model interactions between neutrinos and electrons were also determined.
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| 48. |
- Abdallah, J, et al.
(författare)
-
Production of Xi(0)(c) and Xi(b) in Z decays and lifetime measurement of Xi(b)
- 2005
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; C:44, s. 299-309
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Tidskriftsartikel (refereegranskat)abstract
- The charmed strange baryon Xi(c)(0) was searched for in the decay channel Xi(c)(0) -> Xi(-)pi(+), and the beauty strange baryon Xi(b) in the inclusive channel Xi(b) -> Xi(-)l(-)(nu) over barX, using the 3.5 million hadronic Z events collected by the DELPHI experiment in the years 1992-1995. The Xi(-) was reconstructed through the decay AT, using a constrained fit method for cascade decays. An iterative discriminant analysis was used for the Xi(c)(0) and Xi(b) selection. The production rates were measured to be f(Xi c)(0) x BR(Xi(c)(0) -> Xi(-)pi(+) = (4.7 +/- 1.4(stat.) +/- 1.1(syst.)) x 10(-4) per hadronic Z decay, and BR(b -> Xi(b))xBR(Xi(b) -> Xi(-)l(-)X) = (3.0 +/- 1.0(stat.) +/- 0.3(syst.)) x 10(-4) for each lepton species (electron or muon). The lifetime of the Xi(b) baryon was measured to be tau(Xi b) = 1.45(-0.43)(+0.55)(stat.)+/- 0.13(syst.) ps. A combination with the previous DELPHI lifetime measurement gives tau(Xi b) = 1.48(-0.31)(+0.40)(stat.)+/- 0.12(syst.) ps.
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| 49. |
- Abdallah, J, et al.
(författare)
-
Search for B-s(0)-(B-s(0))over-bar oscillations in DELPHI using high-p(t) leptons
- 2004
-
Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 35:1, s. 35-52
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Tidskriftsartikel (refereegranskat)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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| 50. |
- Abdallah, J, et al.
(författare)
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Search for fermiophobic Higgs bosons in final states with photons at LEP 2
- 2004
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 35:3, s. 313-324
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Tidskriftsartikel (refereegranskat)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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