| 1. |
- Abdallah, J, et al.
(författare)
-
Rapidity-alignment and p(T) compensation of particle pairs in hadronic Z(0) decays
- 2002
-
Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 533:3-4, s. 243-252
-
Tidskriftsartikel (refereegranskat)abstract
- Observation is made of rapidity-alignment of K+K- and (p) over barp pairs which results from their asymmetric orientation in rapidity, with respect to the direction from primary quark to antiquark. The K+K- and (p) over barp data are consistent with predictions from the fragmentation string model. However, the (p) over barp data strongly disagree with the conventional implementation of the cluster model. The non-perturbative process of 'gluon splitting to diquarks' has to be incorporated into the cluster model for it to agree with the data. Local conservation of PT between particles nearby in rapidity (i.e., p(T) compensation) is analysed with respect to the thrust direction for pi(+)pi(-), K+K-, and (p) over barp pairs. In this case, the string model provides fair agreement with the data. The cluster model is incompatible with the data for all three particle pairs. The model with its central premiss of isotropically-decaying clusters predicts a p(T) correlation not seen in the data. (C) 2002 Elsevier Science B.V. All rights reserved.
|
|
| 2. |
- Abdallah, J, et al.
(författare)
-
Search for charged Higgs bosons in e(+)e(-) collisions root s=189-202 GeV
- 2002
-
Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 525:1-2, s. 17-28
-
Tidskriftsartikel (refereegranskat)abstract
- A search for pair-produced charged Higgs bosons was performed in the high energy data collected by the DELPHI detector at LEP II at centre-of-mass energies from 189 GeV to 202 GeV. The three different final states, taunutaunu, c (s) over bar(c) over bars and c (s) over bar taunu were considered. New methods were applied to reject wrong hadronic jet pairings and for the tau identification, where a discriminator based on tau polarisation and polar angles was used. No excess of data compared to the expected Standard Model processes was observed and the existence of a charged Higgs boson with mass lower than 71.5 GeV/c(2) is excluded at the 95% confidence level. (C) 2002 Published by Elsevier Science B.V.
|
|
| 3. |
- Abdallah, J, et al.
(författare)
-
Searches for neutral Higgs bosons in e(+)e(-), collisions from root s=191.6 to 201.7 GeV
- 2002
-
Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 23:3, s. 409-435
-
Tidskriftsartikel (refereegranskat)abstract
- Neutral Higgs bosons of the Standard Model (SM) and the Minimal Supersymmetric Standard Model (MSSM) were searched for in the data collected in 1999 by the DELPHI experiment at centre-of-mass energies between 191.6 and 201.7 GeV with a total integrated luminosity of 228 pb(-1). These analyses, in combination with our results at lower energies, set 95% confidence level lower mass bounds on the Standard Model Higgs boson (107.3 GeV/c(2)) and on the lightest neutral scalar (85.9 GeV/c(2)) and neutral pseudoscalar (86.5 GeV/c(2)) Higgs bosons in representative scans of the MSSM parameter space. An extended scan of the MSSM parameter space was also performed to test the robustness of these limits.
|
|
| 4. |
- Abdallah, J, et al.
(författare)
-
Study of inclusive J/psi production in two-photon collisions at LEP II with the DELPHI detector
- 2003
-
Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 565:1-4, s. 76-86
-
Tidskriftsartikel (refereegranskat)abstract
- Inclusive J/psi production in photon-photon collisions has been observed at LEP II beam energies. A clear signal from the reaction gammagamma --> J/psi + X is seen. The number of observed N(J/psi --> mu(+)mu(-)) events is 36+/-7 for an integrated luminosity of 617 pb(-1), yielding a cross-section of sigma(J/psi + X) = 45+/-9(stat) +/- 17(syst) pb. Based on a study of the event shapes of different types of gammagamma processes in the PYTHIA program, we conclude that (74+/-22) % of the observed J/psi events are due to 'resolved' photons, the dominant contribution of which is most probably due to the gluon content of the photon. (C) 2003 Published by Elsevier B.V.
|
|
| 5. |
- Abreu, P, et al.
(författare)
-
b-tagging in DELPHI at LEP
- 2004
-
Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 32:2, s. 185-208
-
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.
|
|
| 6. |
- Abreu, P., et al.
(författare)
-
Measurement of the mass and width of the W boson in e+e- collisions at √s = 189 GeV
- 2001
-
Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 511:2-4, s. 159-177
-
Tidskriftsartikel (refereegranskat)abstract
- A measurement of the W mass and width has been performed by the DELPHI Collaboration using the data collected during 1998. The data sample has an integrated luminosity of 155 pb-1 and an average centre-of-mass energy of 188.6 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- → lvlqq′ and W+W- → qq′qq′ channels. The W mass result for the 1998 data set is MW = 80.387 ± 0.087(stat) ± 0.034(syst) ± 0.017(LEP) ± 0.035(FSI) GeV/c2, where FSI represents the uncertainty due to final state interaction effects in the qq′qq′ channel, and LEP represents that arising from the knowledge of the beam energy of the accelerator. Combining this result with those previously published by the DELPHI Collaboration gives the result MW = 80.359 ± 0.074(stat) ± 0.032(syst) ± 0.017(LEP) ± 0.033(FSI) GeV/c2. The combined value for the W width is λW = 2.266 ± 0.176(stat)± 0.056(syst)± 0.052(FSI) GeV/c2.
|
|
| 7. |
- Almehed, Sverker, et al.
(författare)
-
A Silicon-Tungsten Electromagnetic Calorimeter for LEP
- 1991
-
Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 305:2, s. 320-330
-
Tidskriftsartikel (refereegranskat)abstract
- This report describes a silicon-tungsten electromagnetic calorimeter used to determine some beam properties and luminosity in the DELPHI experiment at LEP. The polar angular range covered by this detector is 5–8 mrad, which allows the detection of a Bhabha rate about 10 times the rate of produced Z particles at the peak cross section.
|
|
| 8. |
|
|
| 9. |
- Almehed, Sverker, et al.
(författare)
-
Regional research exploitation of the LHC: A case-study of the required computing resources
- 2002
-
Ingår i: Computer Physics Communications. - 0010-4655. ; 145:3, s. 341-350
-
Tidskriftsartikel (refereegranskat)abstract
- A simulation study to evaluate the required computing resources for a research exploitation of the Large Hadron Collider (LHC) has been performed. The evaluation,vas done as a case study. assuming existence of a Nordic regional centre and using the requirements for per-forming a specific physics analysis as a yard-stick. Other input parameters were: assumption for the distribution of researchers at the institutions involved, an analysis model, and two different functional structures of the computing resources.
|
|
| 10. |
- Nygren, Andreas, et al.
(författare)
-
Total cross-section measurements in gamma gamma collisions at very low Q(2) at LEP2
- 2002
-
Ingår i: Photon 2001. - 9789812380531 ; , s. 158-161
-
Konferensbidrag (refereegranskat)abstract
- The multihadron production in the reaction e(+)e(-) -> e(+)e(-) + hadrons has been studied for the first time at LEP2 energies with both scattered e(+) and e(-) detected at very low Q(2), measured by the DELPHI VSAT. A reasonable agreement between data and full simulation is demonstrated and the total gamma gamma hadronic cross-section is estimated for the gamma gamma center of mass energy up to 100 GeV.
|
|
