| 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. |
- Schael, S., et al.
(författare)
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Electroweak measurements in electron positron collisions at W-boson-pair energies at LEP
- 2013
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Ingår i: Physics Reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 532:4, s. 119-244
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Forskningsöversikt (refereegranskat)abstract
- Electroweak measurements performed with data taken at the electron positron collider LEP at CERN from 1995 to 2000 are reported. The combined data set considered in this report corresponds to a total luminosity of about 3 fb(-1) collected by the four LEP experiments ALEPH, DELPHI, 13 and OPAL, at centre-of-mass energies ranging from 130 GeV to 209 GeV. Combining the published results of the four LEP experiments, the measurements include total and differential cross-sections in photon-pair, fermion-pair and four-fermion production, the latter resulting from both double-resonant WW and ZZ production as well as singly resonant production. Total and differential cross-sections are measured precisely, providing a stringent test of the Standard Model at centre-of-mass energies never explored before in electron positron collisions. Final-state interaction effects in four-fermion production, such as those arising from colour reconnection and Bose Einstein correlations between the two W decay systems arising in WW production, are searched for and upper limits on the strength of possible effects are obtained. The data are used to determine fundamental properties of the W boson and the electroweak theory. Among others, the mass and width of the W boson, m(w) and Gamma(w), the branching fraction of W decays to hadrons, B(W -> had), and the trilinear gauge-boson self-couplings g(1)(Z), K-gamma and lambda(gamma), are determined to be: m(w) = 80.376 +/- 0.033 GeV Gamma(w) = 2.195 +/- 0.083 GeV B(W -> had) = 67.41 +/- 0.27% g(1)(Z) = 0.984(-0.020)(+0.018) K-gamma - 0.982 +/- 0.042 lambda(gamma) = 0.022 +/- 0.019. (C) 2013 Elsevier B.V. All rights reserved.
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| 3. |
- Uche, E. O., et al.
(författare)
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Pediatric brain tumor care in a Sub-Saharan setting: current poise of a precariously loaded dice
- 2021
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Ingår i: British Journal of Neurosurgery. - : Informa UK Limited. - 0268-8697 .- 1360-046X. ; 35:2, s. 174-180
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To evaluate the current status of pediatric brain tumor (PBT) care and identify determinants and profiles of survival and school attendance Methods: An 8-year institution-based prospective longitudinal study. All cases investigated with neuroimaging and treated were enrolled. Data was analyzed with SPSS (Inc) Chicago IL, USA version 23. Chi Square test, One-way ANOVA and confidence limits were used to evaluate associations at the 95% level of significance. Ethical approval for our study was obtained Health Research Ethics Committee of our hospital. Results: Among 103 patients enrolled, 92 satisfied our study criteria. There were 45 males and 39 females, M: F = 0.8. The mean age was 9.5 ± 2.1 years 95%CI with a range of 7 months to 16 years. The most common symptom was headache for supratentorial lesions (73%) and gait disturbance (80.2%) for infratentorial lesions. More tumors were supratentorial in location 51 (55.4%), 35 (38.1%) were infratentorial and 6 (6.5%) were transtentorial. Craniopharyngiomas (n = 23), medulloblastomas (n = 22) and astrocytomas (n = 15) were the most common tumors. Hemoglobin genotype (AA and AS) had some influence on tumor phenotype FT, P = 0.033. 76 cases were microsurgically resected while 16 patients were treated with radiotherapy alone. The 30-day mortality for operated cases is 7.2 ± 0.7%. Overall 1-year and 5-year survival was 66.7 and 52.3%, respectively. School attendance, performance and outcome varied among treatment subgroups. Conclusion: Survival profile in this series suggests some improvement in comparison to previous studies from our region, Hemoglobin genotype profiles may signature paediatric brain tumor phenotypes in our setting. © 2020, © 2020 The Neurosurgical Foundation.
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