| 1. |
- Schael, S, et al.
(författare)
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Precision electroweak measurements on the Z resonance
- 2006
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Ingår i: Physics Reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 427:5-6, s. 257-454
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Forskningsöversikt (refereegranskat)abstract
- We report on the final electroweak measurements performed with data taken at the Z resonance by the experiments operating at the electron-positron colliders SLC and LEP. The data consist of 17 million Z decays accumulated by the ALEPH, DELPHI, L3 and OPAL experiments at LEP, and 600 thousand Z decays by the SLID experiment using a polarised beam at SLC. The measurements include cross-sections, forward-backward asymmetries and polarised asymmetries. The mass and width of the Z boson, m(Z) and Gamma(Z), and its couplings to fermions, for example the p parameter and the effective electroweak mixing angle for leptons, are precisely measured: m(Z) = 91.1875 +/- 0.0021 GeV, Gamma(Z) = 2.4952 +/- 0.0023 GeV, rho(l) = 1.0050 +/- 0.0010, sin(2)theta(eff)(lept) = 0.23153 +/- 0.00016. The number of light neutrino species is determined to be 2.9840 +/- 0.0082, in agreement with the three observed generations of fundamental fermions. The results are compared to the predictions of the Standard Model (SM). At the Z-pole, electroweak radiative corrections beyond the running of the QED and QCD coupling constants are observed with a significance of five standard deviations, and in agreement with the Standard Model. Of the many Z-pole measurements, the forward-backward asymmetry in b-quark production shows the largest difference with respect to its SM expectation, at the level of 2.8 standard deviations. Through radiative corrections evaluated in the framework of the Standard Model, the Z-pole data are also used to predict the mass of the top quark, m(t) = 173(+10)(+13) GeV, and the mass of the W boson, m(W) = 80.363 +/- 0.032 GeV. These indirect constraints are compared to the direct measurements, providing a stringent test of the SM. Using in addition the direct measurements of m(t) and m(W), the mass of the as yet unobserved SM Higgs boson is predicted with a relative uncertainty of about 50% and found to be less than 285 GeV at 95% confidence level. (c) 2006 Elsevier B.V. All rights reserved.
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| 2. |
- Aamodt, K., et al.
(författare)
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The ALICE experiment at the CERN LHC
- 2008
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 3:S08002
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Forskningsöversikt (refereegranskat)abstract
- ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-ion detector at the CERN LHC which focuses on QCD, the strong-interaction sector of the Standard Model. It is designed to address the physics of strongly interacting matter and the quark-gluon plasma at extreme values of energy density and temperature in nucleus-nucleus collisions. Besides running with Pb ions, the physics programme includes collisions with lighter ions, lower energy running and dedicated proton-nucleus runs. ALICE will also take data with proton beams at the top LHC energy to collect reference data for the heavy-ion programme and to address several QCD topics for which ALICE is complementary to the other LHC detectors. The ALICE detector has been built by a collaboration including currently over 1000 physicists and engineers from 105 Institutes in 30 countries, Its overall dimensions are 16 x 16 x 26 m(3) with a total weight of approximately 10 000 t. The experiment consists of 18 different detector systems each with its own specific technology choice and design constraints, driven both by the physics requirements and the experimental conditions expected at LHC. The most stringent design constraint is to cope with the extreme particle multiplicity anticipated in central Pb-Pb collisions. The different subsystems were optimized to provide high-momentum resolution as well as excellent Particle Identification (PID) over a broad range in momentum, up to the highest multiplicities predicted for LHC. This will allow for comprehensive studies of hadrons, electrons, muons, and photons produced in the collision of heavy nuclei. Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception of parts of the Photon Spectrometer (PHOS), Transition Radiation Detector (TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will be completed for the high-luminosity ion run expected in 2010. This paper describes in detail the detector components as installed for the first data taking in the summer of 2008.
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| 3. |
- Allison, J, et al.
(författare)
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Geant4 developments and applications
- 2006
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Ingår i: IEEE TRANSACTIONS ON NUCLEAR SCIENCE. - 0018-9499. ; 53:1, s. 270-278
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 4. |
- Torrisi, Lorenzo, et al.
(författare)
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Single crystal silicon carbide detector of emitted ions and soft x rays from power laser-generated plasmas
- 2009
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Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 105, s. 123304-1-123304-7
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Tidskriftsartikel (refereegranskat)abstract
- A single-crystal silicon carbide SiC detector was used for measurements of soft x rays, electrons, and ion emission from laser-generated plasma obtained with the use of the Prague Asterix Laser System PALS at intensities of the order of 1016 W/cm2 and pulse duration of 300 ps. Measurements were performed by varying the laser intensity and the nature of the irradiated target. The spectra obtained by using the SiC detector show not only the photopeak due to UV and softx-ray detection, but also various peaks due to the detection of energetic charged particles. Time-of-flight technique was employed to determine the ion kinetic energy of particles emitted from the plasma and to perform a comparison between SiC and traditional ion collectors. The detector was also employed by inserting absorber films of different thickness in front of the SiC surface inorder to determine, as a first approximation, the mean energy of the soft x-ray emission from the plasma.
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| 5. |
- Beurskens, M. N. A., et al.
(författare)
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Pedestal width and ELM size identity studies in JET and DIII-D; implications for ITER
- 2009
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 0741-3335 .- 1361-6587. ; 51:12, s. 124051-
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Tidskriftsartikel (refereegranskat)abstract
- The dependence of the H-mode edge transport barrier width on normalized ion gyroradius (rho* = rho/a) in discharges with type I ELMs was examined in experiments combining data for the JET and DIII-D tokamaks. The plasma configuration as well as the local normalized pressure (beta), collisionality (nu*), Mach number and the ratio of ion and electron temperature at the pedestal top were kept constant, while rho* was varied by a factor of four. The width of the steep gradient region of the electron temperature (T-e) and density (n(e)) pedestals normalized to machine size showed no or only a weak trend with rho*. A rho(1/2) or rho(1) dependence of the pedestal width, given by some theoretical predictions, is not supported by the current experiments. This is encouraging for the pedestal scaling towards ITER as it operates at lower rho* than existing devices. Some differences in pedestal structure and ELM behaviour were, however, found between the devices; in the DIII-D discharges, the n(e) and T-e pedestal were aligned at high rho* but the ne pedestal shifted outwards in radius relative to T-e as rho* decreases, while on JET the profiles remained aligned while rho* was scanned by a factor of two. The energy loss at an ELM normalized to the pedestal energy increased from 10% to 40% as rho* increased by a factor of two in the DIII-D discharges but no such variation was observed in the case of JET. The measured pedestal pressures and widths were found to be consistent with the predictions from modelling based on peeling-ballooning stability theory, and are used to make projections towards ITER
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| 8. |
- Brunsell, Per, et al.
(författare)
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Resistive wall mode feedback control experiments in EXTRAP T2R
- 2007
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Ingår i: 34th EPS Conference on Plasma Physics 2007, EPS 2007 - Europhysics Conference Abstracts. - 9781622763344 ; , s. 544-547
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Konferensbidrag (refereegranskat)abstract
- Experiments in EXTRAP T2R on RWM stabilization using intelligent shell feedback with a P-controller showed that mode suppression improves with increasing gain up to the system stability limit. A PD-controller gives faster response and allows operation with higher gain. The PI-controller is useful for suppression of modes driven by external resonant field error. Best mode suppression was in the present study achieved with a PID-controller.
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| 9. |
- Börjesson, Pål, et al.
(författare)
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Hållbara drivmedel - finns de?
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Vårt syfte med denna rapport är att diskutera drivmedel från ett brett perspektiv ur hållbarhetssynpunkt. Biodrivmedel och el analyseras och jämförs med fossila drivmedel. Vår målsättning är att försöka peka ut under vilka förutsättningar som drivmedel kan anses försvarbara ur hållbarhetssynpunkt och vilka system som vi bör utveckla respektive vilka system som vi bör undvika. En övergripande slutsats i studien är att man inte kan fastställa hur hållbara biodrivmedel blir i framtiden utan att samtidigt beakta skala och tillväxttakt. Dagens biodrivmedel i Sverige är hållbara utifrån den aktuella produktionsvolymen och gynnar utvecklingen av nya drivmedelssystem, men man bör ställa hårda krav på energi- och klimateffektivitet i hela bränslekedjan (från odling till tank) vid ökade produktionsvolymer. Det är av hög prioritet att utveckla bränslesnåla bilar och här kommer elhybridteknologin och elbilar att bli allt viktigare. En långsiktig strategi för biodrivmedel bör innehålla satsningar på teknologi både för termisk förgasning och biologiska omvandlingsmetoder för lignocellulosa eftersom detta är kompletterande lika mycket som konkurrerande teknologier samt ger större flexibilitet och mindre risk för konflikter. Biogas från restprodukter har stora miljöfördelar och kan expandera med liten risk för konflikter. Certifiering (rätt utformat) är ett viktigt och nödvändigt verktyg på vägen mot mer hållbara drivmedel och vid ökade produktionsvolymer, men dessa system ska inte överskattas då de aldrig kan innefatta alla hållbarhetskriterier. Socio-ekonomiska aspekter som arbetsförhållanden, lokal landsbygdsutveckling osv samt effekter av ökad markkonkurrens måste i första hand lösas med generella åtgärder som nationell lagstiftning, fördelningspolitik, program och planer som i sin tur bör stödjas av internationella avtal och utvecklingssamarbete på olika nivåer. Oavsett utvecklingen i Sverige eller EU så kommer biodrivmedelsproduktionen globalt att öka, framför allt i utvecklingsländerna. Det är därför viktigt att ta vara på den möjlighet vi har idag att medverka i utvecklingen och införandet av hållbarhetskriterier. Förnybara drivmedel kan, med rätt utformning och styrmedel för lämplig tillväxttakt och produktionsvolym, leda till en positiv och hållbar utveckling i både industri- och utvecklingsländer.
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| 10. |
- Börjesson, Pål, et al.
(författare)
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Sustainable vehicle fuels - do they exist?
- 2009
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Our aim with this report is to discuss vehicle fuels from a wide perspective of sustainability. Biofuels and electricity are analyzed and compared to fossil vehicle fuels. Our goal is to try to point out the circumstances under which vehicle fuels can be reasonably perceived as sustainable, and which systems we should develop and which we should avoid. The all-embracing conclusion of this study is that one can not establish how sustainable fuels will develop in the future without simultaneously taking into consideration both scale and pace of growth. Today’s biofuels produced in Sweden are sustainable, given the present production volume, and promote further development of new fuel systems. However, in the case of increased production volumes, exact requirements should be established for the energy- and climate efficiency of the entire fuel chain (from cultivation to tank). High priority should be given to the development of fuel-efficient cars. In this field hybrid electric technology and electric cars will grow in importance. Any long-term strategy for biofuels should include investments in technology for both thermal gasification and biological conversion methods of lignocellulose, since these are complementing as much as competing technologies, both increasing the flexibility as well as decreasing the risk of conflicts. Biogas from waste products has great environmental advantages and the sector can be expanded with only small risks of conflicts. Certification (if correctly formulated) is an important and necessary tool on the way towards more sustainable vehicle fuels and increased production volumes, but certification systems should not be overrated since they can not cover all sustainability aspects. Socio-economic aspects such as working conditions, local rural development etc. must be dealt with through general measures such as national laws, distribution policies, programs and plans, all of which should be supported by international agreements and cooperation on development at all levels. Irrespective of the development in Sweden or the EU, global production of biofuels will increase, not least in the developing countries. It is therefore important to exploit the opportunity we have today to participate in the development and implementation of sustainability criteria. Renewable vehicle fuels can lead to a positive as well as sustainable development in both industrialized and developing countries, when the framing and guidance for an adequate pace of growth and production volumes are given.
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