| 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.
|
|
| 4. |
- Knutsson, M., et al.
(författare)
-
On Extraction Of Ic-Engine Intake Acoustic Source Data From Non-Linear Simulations
- 2005
-
Ingår i: Proceedings of the 12th International Congress on Sound and Vibration (ICSV12) Lisbon, Portugal, International Congress on Sound and Vibration. - 9781627481496 ; , s. 2263-2270
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Non linear 1-D CFD time domain prediction codes are used for calculation of performance of the gas exchange process for IC-engines. These codes give time varying pressures and velocities in the exhaust and intake system. They could therefore in principle be used to predict radiated orifice noise. The accuracy is however not sufficient for using them as a virtual design tool. Using linear three dimensional frequency domain codes, more accurate results might be provided for complicated geometries. Radiated shell noise and frequency dependent damping could also be included in the frequency domain models. To calculate insertion loss of air-cleaner systems or the level of radiated intake orifice and shell noise, information about the engine as an acoustic source is needed. The source model used in the low frequency plane wave range for simulation of dominating engine harmonics is the linear time invariant 1-port model. The acoustic source data is usually obtained from experimental tests where the multi-load methods and especially the two-load method are most commonly used. These tests are time consuming, expensive and require physical hardware and can therefore not be used for early predictions. It would therefore be of interest to extract the acoustic source data from existing 1-D CFD gas exchange codes. This paper presents a comparison between results obtained applying the two-load technique to measurements on a six-cylinder personal car petrol engine and to 1-D simulations of identical intake systems on the same engine. The results show that it is possible to obtain reasonably accurate source strength as well as source impedance estimates for the intake side from 1-D gas exchange simulations.
|
|
