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- 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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| 3. |
- Morton, LM, et al.
(författare)
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Hepatitis C virus infection and risk of posttransplantation lymphoproliferative disorder among solid organ transplant recipients
- 2007
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Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 110:13, s. 4599-4605
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Tidskriftsartikel (refereegranskat)abstract
- Posttransplantation lymphoproliferative disorder (PTLD) is a serious complication of solid organ transplantation. Hepatitis C virus (HCV) infection has been linked to increased risk of lymphoma among immunocompetent individuals. We therefore investigated the association between HCV infection and PTLD in a retrospective cohort study of all individuals in the United States who received their first solid organ transplant from 1994 to 2005 (N = 210 763) using Scientific Registry of Transplant Recipients data. During follow-up, 1630 patients with PTLD were diagnosed. HCV prevalence at transplantation was 11.3%. HCV infection did not increase PTLD risk in the total cohort (Cox regression model, hazard ratio [HR] = 0.84; 95% confidence interval [CI] 0.68-1.05), even after adjustment for type of organ transplanted, indication for transplantation, degree of HLA mismatch, donor type, or use of immunosuppression medications. Additional analyses also revealed no association by PTLD subtype (defined by site, pathology, cell type, and tumor Epstein-Barr virus [EBV] status). HCV infection did increase PTLD risk among the 2.8% of patients (N = 5959) who were not reported to have received immunosuppression maintenance medications prior to hospital discharge (HR = 3.09; 95% CI, 1.14-8.42; P interaction = .007). Our findings suggest that HCV is not a major risk factor for PTLD, which is consistent with the model in which an intact immune system is necessary for development of HCV-related lymphoproliferation.
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