| 1. |
- Schael, S, et al.
(författare)
-
Precision electroweak measurements on the Z resonance
- 2006
-
Ingår i: Physics Reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 427:5-6, s. 257-454
-
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.
|
|
| 2. |
- Abazov, V. M., et al.
(författare)
-
The upgraded DO detector
- 2006
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 565:2, s. 463-537
-
Tidskriftsartikel (refereegranskat)abstract
- The DO experiment enjoyed a very successful data-collection run at the Fermilab Tevatron collider between 1992 and 1996. Since then, the detector has been upgraded to take advantage of improvements to the Tevatron and to enhance its physics capabilities. We describe the new elements of the detector, including the silicon microstrip tracker, central fiber tracker, solenoidal magnet, preshower detectors, forward muon detector, and forward proton detector. The uranium/liquid -argon calorimeters and central muon detector, remaining from Run 1, are discussed briefly. We also present the associated electronics, triggering, and data acquisition systems, along with the design and implementation of software specific to DO.
|
|
| 3. |
- Abate, E., et al.
(författare)
-
Combined performance tests before installation of the ATLAS Semiconductor and Transition Radiation Tracking Detectors
- 2008
-
Ingår i: Journal of Instrumentation. - 1748-0221. ; 3
-
Tidskriftsartikel (refereegranskat)abstract
- The ATLAS (A Toroidal LHC ApparatuS) Inner Detector provides charged particle tracking in the centre of the ATLAS experiment at the Large Hadron Collider (LHC). The Inner Detector consists of three subdetectors: the Pixel Detector, the Semiconductor Tracker (SCT), and the Transition Radiation Tracker (TRT). This paper summarizes the tests that were carried out at the final stage of SCT+TRT integration prior to their installation in ATLAS. The combined operation and performance of the SCT and TRT barrel and endcap detectors was investigated through a series of noise tests, and by recording the tracks of cosmic rays. This was a crucial test of hardware and software of the combined tracker detector systems. The results of noise and cross-talk tests on the SCT and TRT in their final assembled configuration, using final readout and supply hardware and software, are reported. The reconstruction and analysis of the recorded cosmic tracks allowed testing of the offline analysis chain and verification of basic tracker performance parameters, such as efficiency and spatial resolution, in combined operation before installation.
|
|
| 4. |
- Abdesselam, A., et al.
(författare)
-
The ATLAS semiconductor tracker end-cap module
- 2007
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 575:3, s. 353-389
-
Tidskriftsartikel (refereegranskat)abstract
- The challenges for the tracking detector systems at the LHC are unprecedented in terms of the number of channels, the required read-out speed and the expected radiation levels. The ATLAS Semiconductor Tracker. (SCT) end-caps have a total of about 3 million electronics channels each reading out every 25 ns into its own on-chip 3.3 mu s buffer. The highest anticipated dose after 10 years operation is 1.4x10(14) cm(-2) in units of 1 MeV neutron equivalent (assuming the damage factors scale with the non-ionising energy loss). The forward tracker has 1976 double-sided modules, mostly of area similar to 70 cm(2), each having 2 x 768 strips read out by six ASICs per side. The requirement to achieve an average perpendicular radiation length of 1.5% X-0, while coping with up to 7 W dissipation per module (after irradiation), leads to stringent constraints on the thermal design. The additional requirement of 1500e(-) equivalent noise charge (ENC) rising to only 1800e(-) ENC after irradiation, provides stringent design constraints on both the high-density Cu/Polyimide flex read-out circuit and the ABCD3TA read-out ASICs. Finally, the accuracy of module assembly must not compromise the 16 mu m (r phi) resolution perpendicular to the strip directions or 580 mu m radial resolution coming from the 40 mrad front-back stereo angle. A total of 2210 modules were built to the tight tolerances and specifications required for the SCT. This was 234 more than the 1976 required and represents a yield of 93%. The component flow was at times tight, but the module production rate of 40-50 per week was maintained despite this. The distributed production was not found to be a major logistical problem and it allowed additional flexibility to take advantage of where the effort was available, including any spare capacity, for building the end-cap modules. The collaboration that produced the ATLAS SCT end-cap modules kept in close contact at all times so that the effects of shortages or stoppages at different sites could be rapidly resolved.
|
|
| 5. |
- Wilson, J. A., et al.
(författare)
-
The optical links of the ATLAS SemiConductor tracker
- 2007
-
Ingår i: Journal of Instrumentation. - 1748-0221. ; 2, s. 1-28
-
Tidskriftsartikel (refereegranskat)abstract
- Optical links are used for the readout of the 4088 silicon microstrip modules that make up the SemiConductor Tracker of the ATLAS experiment at the CERN Large Hadron Collider (LHC). The optical link requirements are reviewed, with particular emphasis on the very demanding environment at the LHC. The on-detector components have to operate in high radiation levels for 10 years, with no maintenance, and there are very strict requirements on power consumption, material and space. A novel concept for the packaging of the on-detector optoelectronics has been developed to meet these requirements. The system architecture, including its redundancy features, is explained and the critical on-detector components are described. The results of the extensive Quality Assurance performed during all steps of the assembly are discussed.
|
|
| 6. |
- Birney, Ewan, et al.
(författare)
-
Identification and analysis of functional elements in 1% of the human genome by the ENCODE pilot project
- 2007
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 447:7146, s. 799-816
-
Tidskriftsartikel (refereegranskat)abstract
- We report the generation and analysis of functional data from multiple, diverse experiments performed on a targeted 1% of the human genome as part of the pilot phase of the ENCODE Project. These data have been further integrated and augmented by a number of evolutionary and computational analyses. Together, our results advance the collective knowledge about human genome function in several major areas. First, our studies provide convincing evidence that the genome is pervasively transcribed, such that the majority of its bases can be found in primary transcripts, including non-protein-coding transcripts, and those that extensively overlap one another. Second, systematic examination of transcriptional regulation has yielded new understanding about transcription start sites, including their relationship to specific regulatory sequences and features of chromatin accessibility and histone modification. Third, a more sophisticated view of chromatin structure has emerged, including its inter-relationship with DNA replication and transcriptional regulation. Finally, integration of these new sources of information, in particular with respect to mammalian evolution based on inter- and intra-species sequence comparisons, has yielded new mechanistic and evolutionary insights concerning the functional landscape of the human genome. Together, these studies are defining a path for pursuit of a more comprehensive characterization of human genome function.
|
|
| 7. |
- Ryk, C., et al.
(författare)
-
Influence of GSTM1, GSTT1, GSTP1 and NAT2 genotypes on the p53 mutational spectrum in bladder tumours
- 2005
-
Ingår i: Int J Cancer. - 0020-7136. ; 113:5, s. 761-8
-
Tidskriftsartikel (refereegranskat)abstract
- Genetic polymorphisms affecting expression or activity of the corresponding enzymes can influence the risk of acquiring gene mutations and various cancers. We have studied 327 bladder cancer patients with regard to the functionally related polymorphisms of GSTM1, GSTT1, GSTP1 and NAT2 and analysed the p53 mutational status of their tumours. Fifty p53 mutations, 26% transversions and 74% transitions, were detected in 44 patients. P53 mutation frequency was significantly higher in higher-grade tumours than in low-grade tumours (OR = 2.09, 95% CI 1.44-3.02, adjusted for age and sex). Also, a significant association was found between tumour stage (Tis and T2+ vs. Ta and T1) and presence of the GSTP1 val allele (adjusted OR = 2.00, CI 1.14-3.52). Overall, there was no significant difference in frequency of p53 mutation among patients with different genotypes. Among patients with p53 mutation, transversions were significantly more frequent in GSTM1-negative as compared to GSTM1-positive individuals (OR = 5.18, CI 1.07-25.02, adjusted for age, sex and tumour stage). With one exception, all tumours with the most common type of transversion, G:C-C:G, occurred in GSTM1-negative patients. Among smokers, all transversions (3 of 3), but only 2 of 13 transitions, were found among carriers of the GSTP1 variant allele, and samples carrying at least 1 variant GSTP1 allele had more transitions at CpG sites than wild-type samples (adjusted OR = 4.61, CI 0.82-26.04). No significant associations were found for the NAT2 gene. Our results suggest that impaired glutathione conjugation may affect the mutation spectrum in critical target genes.
|
|
| 8. |
|
|
| 9. |
- Ryk, C., et al.
(författare)
-
Influence of polymorphism in DNA repair and defence genes on p53 mutations in bladder tumours
- 2006
-
Ingår i: Cancer Lett. - : Elsevier BV. - 0304-3835 .- 1872-7980. ; 241:1, s. 142-9
-
Tidskriftsartikel (refereegranskat)abstract
- We studied the effects of polymorphisms in nine genes involved in DNA repair and detoxification on occurrence and type of p53 mutation in 327 bladder cancer patients. The included polymorphisms are XPC(Lys939Gln), XPD(Lys751Gln), XPG(Asp1104His), XRCC1(Arg3999Gln), XRCC3(Thr241Met), NBS1(Glu185Gln), cyclin D1(Pro241Pro), MTHFR(Ala222Val and Glu429Ala) and NQO1(Arg139Trp and Pro187Ser). We found increased risk for p53 mutation among cyclin D1 variant allele homozygotes (OR 2.4 CI 0.8-6.7). Among non-smokers, 75% (3/4) with p53 mutation but only 12.5% (3/24) without p53 mutations were XRCC3 241Met homozygotes (P=0.03). Among smokers, all p53 transversions (3/3), but only 41.7% (5/12) of p53 transitions were found among carriers of the XPC 939Gln allele. Individuals carrying the NQO1 187Ser allele showed increased risk for p53 transversions (OR 4.7, CI 0.9-26.1). All (2/2) NQO1 139Trp allele carriers but only 17.5% (7/40) of the Arg139 homozygotes had p53 transversions. Our findings suggest that altered repair and detoxification due to genetic polymorphism may influence the occurrence of p53 mutations in bladder cancer.
|
|
| 10. |
- Hou, Xiaolin, et al.
(författare)
-
Time series of I-129 and I-127 speciation in precipitation from Denmark
- 2009
-
Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 43:17, s. 6522-6528
-
Tidskriftsartikel (refereegranskat)abstract
- Environmental I-129 mainly released from reprocessing plants at La Hague (France) and Sellafield (UK) provides a unique atmospheric and environmental tracer, This study deals with I-129 and I-127 speciation in precipitation collected in Denmark during 2001-2006 that indicates many new findings. The concentrations of total I-129 in precipitation vary from 0.28 to 5.63 x 10(9) atoms I-129 L-1 with an average of (2.34 +/- 1.43) x 10(9) atoms I-129 L-1, and the annual deposition flux of I-129 is (1.25 +/- 0.30) x 10(12) atoms m(-2). increased I-129 levels in precipitation and I-129/I-127 ratio are attributed to the releases of I-129 from the reprocessing plants at La Hague and Sellafield. Iodide is the major specie of I-129, which accounts for 50-99% of tote I-129. The concentrations of total I-129 vary from 0.78 to 2.70 mu g iodine L-1 with an average of 1.63 +/- 0.47 mu g iodine L-1, and annual deposition flux of 0.95 +/- 0.26 mg m(-2). Unlike I-129, iodate is the major specie of I-127, which accounts for 43-93% of total I-127. The I-129/I-127 atomic ratios for total iodine vary from 5.04 to 76.5 x 10(-8) with an average of (30.1 +/- 16.8) x 10(-8). These values are 10 times lower for iodate with an average of (2.95 +/- 3.13) x 10-8. Seasonal variations of I-129/I-127 values and I-129 concentrations are associated with highs in spring and lows in summer-autumn periods. Re-emission of I-129 from the surface water of the English Channel, Irish Sea, North Sea, and Norwegian Sea, especially from the European continental coast areas, is evidently the major source of I-129 in the precipitation, while stable I-127 in the precipitation has multiple sources, i.e., marine, as well as terrestrial emission. This work shows that data on speciation of iodine isotopes can provide thorough indications about the sources and geochemical cycle despite the complicated atmospheric chemistry of iodine.
|
|
| 11. |
- Hou, Ying, et al.
(författare)
-
Carrier wave-packet transport under the influence of charged quantum dot in small-area resonant tunneling diodes
- 2008
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 93:13, s. 132108-
-
Tidskriftsartikel (refereegranskat)abstract
- It was shown experimentally that charging InAs quantum dots (QDs) embedded in a small-area GaAs/AlAs double-barrier resonant tunneling diode (RTD) effectively modified the carrier transport properties of the RTD. By adopting and comparing the one-dimensional plane-wave and three-dimensional (3D) wave-packet transport theories we show that the electron transports in the QDRTD device are in the form of 3D wave packets, which are strongly affected by the 3D long-range Coulomb potential induced by charged InAs QDs. This explains well experimental data and indicates that the 3D wave-packet transport model is more appropriate for the QDRTD device.
|
|
| 12. |
- Hou, Ying, et al.
(författare)
-
Effects of series and parallel resistances on the current-voltage characteristics of small-area air-bridge resonant tunneling diode
- 2008
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 104:7
-
Tidskriftsartikel (refereegranskat)abstract
- We have studied experimentally and theoretically the effects of series and parallel resistances on the current-voltage (I-V) characteristics of the resonant tunneling diode (RTD) in the format of a small-area freestanding air bridge. It has been shown by standard quantum mechanical considerations that the I-V characteristics consists of a simple resonant current peak (without bistability) and the voltage at the current peak is quite low, whereas experiments show not only a much high current-peak voltage, but also the bistability. Furthermore, experimental peak-to-valley ratio is in general quite low. By analyzing material and device structures, it has been demonstrated that the series resistance in the RTD contacts shifts the peak in current to higher voltage, it also creates the experimentally observed bistability effect in the region of the tunneling resonance. The parallel resistance induces a leakage current and reduces the peak-to-valley ratio. We have further performed similar analyses to many RTD structures reported in the literature and the conclusions remain the same.
|
|
| 13. |
- Hou, Yuanyuan, et al.
(författare)
-
Pressure-induced polymerization of nano- and submicrometer C60 rods into a rhombohedral phase
- 2006
-
Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 423:1-3, s. 215-219
-
Tidskriftsartikel (refereegranskat)abstract
- C-60 rods with nano- and submicrometer dimensions were polymerized at 4.5 GPa and 973 K. Raman spectroscopy showed that the material transformed into a rhombohedral polymeric structure under high pressure and high temperature (HPHT) conditions. The HPHT polymerized samples keep the original rod shape. The position dependence of photoluminescence (PL) spectra have been studied on the rhombohedral polymer C60 rods at room temperature. The intensity of the 1.74 eV peak from the rhombohedral phase varies systematically between the edge of and the middle of the rod. Our results indicate that the 1.74 eV peak originates from surface defects.
|
|
| 14. |
|
|
