| 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. |
- Aaron, F. D., et al.
(författare)
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Multi-leptons with high transverse momentum at HERA
- 2009
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Ingår i: Journal of High Energy Physics. - : Springer Science and Business Media LLC. - 1029-8479. ; :10
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Tidskriftsartikel (refereegranskat)abstract
- Events with at least two high transverse momentum leptons (electrons or muons) are studied using the H1 and ZEUS detectors at HERA with an integrated luminosity of 0.94 fb(-1). The observed numbers of events are in general agreement with the Standard Model predictions. Seven di- and tri-lepton events are observed in e(+)p collision data with a scalar sum of the lepton transverse momenta above 100 GeV while 1.94 +/- 0.17 events are expected. Such events are not observed in e(-)p collisions for which 1.19 +/- 0.12 are predicted. Total visible and differential di-electron and di-muon photoproduction cross sections are extracted in a restricted phase space dominated by photon-photon collisions.
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| 3. |
- Bruzzi, M, et al.
(författare)
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Radiation-hard semiconductor detectors for SuperLHC
- 2005
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 541:1-2, s. 189-201
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Tidskriftsartikel (refereegranskat)abstract
- An option of increasing the luminosity of the Large Hadron Collider (LHC) at CERN to 1035 cm-2 s-1 has been envisaged to extend the physics reach of the machine. An efficient tracking down to a few centimetres from the interaction point will be required to exploit the physics potential of the upgraded LHC. As a consequence, the semiconductor detectors close to the interaction region will receive severe doses of fast hadron irradiation and the inner tracker detectors will need to survive fast hadron fluences of up to above 1016cm-2. The CERN-RD50 project "Development of Radiation Hard Semiconductor Devices for Very High Luminosity Colliders" has been established in 2002 to explore detector materials and technologies that will allow to operate devices up to, or beyond, this limit. The strategies followed by RD50 to enhance the radiation tolerance include the development of new or defect engineered detector materials (SiC, GaN, Czochralski and epitaxial silicon, oxygen enriched Float Zone silicon), the improvement of present detector designs and the understanding of the microscopic defects causing the degradation of the irradiated detectors. The latest advancements within the RD50 collaboration on radiation hard semiconductor detectors will be reviewed and discussed in this work.
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| 4. |
- Chung, S. J., et al.
(författare)
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Time stability of multi-domain states formed in the magnetization reversal process of GaMnAs film
- 2007
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Ingår i: Solid State Communications. - : Elsevier BV. - 0038-1098 .- 1879-2766. ; 143:4-5, s. 232-235
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Tidskriftsartikel (refereegranskat)abstract
- The magnetization reversal process of ferromagnetic GaMnAs epilayers has been systematically investigated using the planar Hall effect (PHE) and magnetoresistance (MR). We have observed non-abrupt transitions between two orientations of magnetization in PHE and striking resistance dips at the second switching in MR. The observed behaviors indicate that multi-domain structures are formed as magnetization undergoes a reorientation. An asymmetric PHE hysteresis loop was obtained when the range of the field scan was restricted to fields below the final magnetization transition. This indicates that the domain structure formed at the moment of magnetization reorientation remains stable even after the magnetic field is removed. The time stability of the multi-domain structure was further tested by monitoring the change in the planar Hall resistance value for more than 24 h.
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| 5. |
- Lebedev, Alexander, 2000-, et al.
(författare)
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A study of thick 3C-SiC epitaxial layers grown on 6H-SiC substrates by sublimation epitaxy in vacuum
- 2007
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Ingår i: Semiconductors (Woodbury, N.Y.). - 1063-7826 .- 1090-6479. ; 41:3, s. 263-265
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Tidskriftsartikel (refereegranskat)abstract
- 3C-SiC epitaxial layers with a thickness of up to 100 μm were grown on 6H-SiC hexagonal substrates by sublimation epitaxy in vacuum. The n-type epitaxial layers with the area in the range 0.3-0.5 cm2 and uncompensated donor concentration N d - N a ∼ (10 17-1018) cm-3 were produced at maximum growth rates of up to 200 μm/h. An X-ray analysis demonstrated that the epitaxial layers are composed of the 3C-SiC polytype, without inclusions of other polytypes. The photoluminescence (PL) spectrum of the layers was found to be dominated by the donor-acceptor (Al-N) recombination band peaked at hv ≈ 2.12 eV. The PL spectrum measured at 6 K was analyzed in detail. It is concluded that the epitaxial layers obtained can serve as substrates for 3C-SiC-based electronic devices. © Nauka/Interperiodica 2007.
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| 6. |
- Lebedev, S.P., et al.
(författare)
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P-type 3C-SiC Grown by Sublimation Epitaxy on 6H-SiC Substrates
- 2009
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Ingår i: ECSCRM2008,2008. - Materials Science Forum Vols. 615-617 : Trans Tech Publications. - 9780878493340 ; , s. 177-180
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Konferensbidrag (refereegranskat)abstract
- Highly doped p-3C-SiC layers of good crystal perfection have been grown by sublimation epitaxy in vacuum. Analysis of the photoluminescence (PL) spectra and temperature dependence of the carrier concentration shows that at least two types of acceptor centers at ~EV + 0.25 eV and at EV + 0.06-0.07 eV exist in the samples studied. A conclusion is made that layers of this kind can be used as p-emitters in 3C-SiC devices.
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| 7. |
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| 8. |
- Yea, S.-y., et al.
(författare)
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Effect of chemical etching on magnetic anisotropy of ferromagnetic GaMnAs films studied by planar Hall effect
- 2008
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Ingår i: Solid State Communications. - : Elsevier BV. - 0038-1098 .- 1879-2766. ; 147:7-8, s. 309-312
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the effect of chemical etching on magnetic anisotropy of ferromagnetic GaMnAs film using the planar Hall effect (PHE). Different thicknesses were obtained on a single GaMnAs specimen by using different etching times on selected areas, and the PHE was then measured using the Hall bar configurations patterned on the area. Cubic and uniaxial anisotropy fields were obtained for the films by fitting the angular dependence of the PHE data to the Stoner-Wohlfarth model. The results exhibited a very systematic dependence on the etched thickness, demonstrating that the chemical etching process significantly affects the magnetic anisotropy of ferromagnetic GaMnAs films.
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