Electroweak tests of the Standard Model (original) (raw)

Tests of the Electroweak Standard Model

Journal of Physics: Conference Series, 2014

Electroweak precision tests of the Standard Model of the fundamental interactions are reviewed ranging from the lowest to the highest energy experiments. Results from global fits are presented with particular emphasis on the extraction of fundamental parameters such as the Fermi constant, the strong coupling constant, the electroweak mixing angle, and the mass of the Higgs boson. Constraints on physics beyond the Standard Model are also discussed.

Electroweak Standard Model and Precision Tests

AIP Conference Proceedings, 2003

I give an introduction and overview of recent developments in high precision tests of the Standard Model. This includes a summary of Z-pole measurements, a brief account of the NuTeV result on neutrino-nucleon scattering, the anomalous magnetic moment of the muon, and implications for the Higgs boson mass.

A Combination of Preliminary Electroweak Measurements and Constraints on the Standard Model

2003

This note presents a combination of published and preliminary electroweak results from the four LEP collaborations and the SLD collaboration which were prepared for the 1996 summer conferences. Averages of the results concerning electroweak physics are presented. They are derived from the measurements of hadronic and leptonic cross sections, the leptonic forward-backward asymmetries, the polarisation asymmetries, the bb and cc partial widths and forward-backward asymmetries and the qq c harge asymmetry. Almost every measurement including the LEP beam energy calibration has been updated with respect to the summer 1995 conferences. The results are compared to precise electroweak measurements from other experiments. The parameters of the Standard Model are evaluated, rst using the combined LEP electroweak measurements, and then using the full set of precise electroweak results. The LEP Collaborations each take responsibility for the preliminary data of their own experiment. y The present members of the LEP Electroweak Working Group are:

Implications of Precision Electroweak Measurements for Physics Beyond the SM

1999

We perform a global analysis of electroweak precision measurements to find constraints on physics beyond the Standard Model. In particular, we discuss oblique parameters, which are useful to constrain additional matter fields, as well as extra ZZZ bosons, and supersymmetry. We also summarize the present information on the Higgs boson mass.

Precision Tests of Electroweak Physics

1999

We review the current status of precision electroweak measurements and the constraints they impose on new physics. We perform a model independent analysis using the STU-formalism of Ref. 1, and then discuss how the Z-pole data from LEP and SLD can be used to constrain models that are not covered within that framework.

Precision Tests of Electroweak Interactions ∗

2008

The status of the precision tests of the electroweak interactions is reviewed in this paper. An emphasis is put on the Standard Model analysis based on measurements at LEP/SLC and the Tevatron. The results of the measurements of the electroweak mixing angle in the NuTeV experiment and the future prospects are discussed. 1

Summary of the Electroweak and Beyond the Standard Model Working Group

2008

A wide array of deep-inelastic-scattering and hadron collider experiments have tested the predictions of the electroweak theory and measured its parameters, while also searching for new particles and processes. We summarise recent measurements and searches that probe the Standard Model to unprecedented precision.

Analysis of electroweak precision data and prospects for future improvements

1998

We update our previous work on an analysis of the electroweak data by including new and partly preliminary data available up to the 1996 summer conferences. The new results on the Z partial decay widths into b and c hadrons now offer a consistent interpretation of all data in the minimal standard model. The value extracted for the strong interaction coupling constant α s (m Z ) agrees well with determinations in other areas. New constraints on the universal parameters S, T and U are obtained from the updated measurements. No signal of new physics is found in the S, T , U analysis once the SM contributions with m t ∼ 175GeV and those of not a too heavy Higgs boson are accounted for. The naive QCD-like technicolor model is now ruled out at the 99%CL even for the minimal model with SU(2) TC . In the absence of a significant new physics effect in the electroweak observables, constraints on masses of the top quark, m t , and Higgs boson, m H , are derived as a function of α s and the QED effective couplingᾱ(m 2 Z ). The preferred range of m H depends rather strongly on the actual value of m t : m H < 360 GeV for m t = 170 GeV, while m H > 130 GeV for m t = 180 GeV at 95 %CL. Prospects due to forthcoming improved measurements of asymmetries, the mass of the weak boson W m W , m t andᾱ(m 2 Z ) are discussed. Anticipating uncertainties of 0.00020 fors 2 (m 2 Z ), 20 MeV for m W , and 2 GeV for m t , the new physics contributions to the S, T , U parameters will be constrained more severely, and, within the SM, the logarithm of the Higgs mass can be constrained to about ±0.35. The better constraints on S, T , U and on m H within the minimal SM should be accompanied with matching precision inᾱ(m 2 Z ).

The W-boson mass and precision tests of the Standard Model

Zeitschrift f�r Physik C Particles and Fields, 1996

We have examined the electroweak radiative corrections in the LEP precision data in view of the new measurements of M W and m t as well as the recent progress in the higher order radiative corrections. From the minimal χ 2-fit to the experimental Z-decay parameters (with the aid of a modified ZFITTER program), we predict that M W = 80.29(4)(2) GeV where the first error is due to the uncertainty in the fitted m t for a fixed m H and the second error comes from the m H in the range of 60−1000 GeV, which is to be compared with the current world average M W = 80.23(18) GeV. The current world average value of M W and the 1994 LEP data definitely favor nonvanishing electroweak radiative corrections and are consistent with a heavy m t as measured by the recent CDF report but with a heavy Higgs scalar of about 400 GeV within the context of the minimal standard model. The sensitivity of and the errors in the best fit solutions due to the uncertainties in the gluonic coupling α s (M Z) and α(M Z) are also studied carefully. In addition we discuss how the future precision measurements of M W can provide a decisive test for the standard model with radiative corrections and give a profound implication for the measurement of t-quark and Higgs masses.

Confronting electroweak precision measurements with New Physics models

The European Physical Journal C, 2000

Precision experiments, such as those performed at LEP and SLC, offer us an excellent opportunity to constrain extended gauge model parameters. To this end, it is often assumed, that in order to obtain more reliable estimates, one should include the sizable one-loop Standard Model (SM) corrections, which modify the Z 0 couplings as well as other observables. This conviction is based on the belief that the higher order contributions from the "extension sector" will be numerically small. However, the structure of higher order corrections can be quite different when comparing the SM with its extension, thus one should avoid assumptions which do not care about such facts. This is the case for all models with ρtree ≡ M 2 W /(M 2 Z cos 2 ΘW ) = 1. As an example, both the manifest left-right symmetric model and the SU (2)L ⊗ U (1)Y ⊗Ũ (1) model, with an additional Z ′ boson, are discussed and special attention to the top contribution to ∆ρ is given. We conclude that the only sensible way to confront a model with the experimental data is to renormalize it self-consistently, if not, parameters which depend strongly on quantum effects should be left free in fits, though essential physics is lost in this way. We should note that arguments given here allow us to state that at the level of loop corrections (indirect effects) there is nothing like a "model independent global analysis" of the data.