LEP EW WG Plots for Winter 2008

Latest corrections and/or modifications 19-March-2008.

You can find here the plots that have been updated for the Winter 2008 conferences. Most results are final, such as the Z-pole measurements from SLD and at LEP. The LEP-2 results on the mass and width of the W boson are final but their combination is still preliminary.

Changes:

All fits on which all plots posted here are based, include the electroweak precision measurements made by SLD and LEP-1 in electron-positron collisions at the Z pole, described in the final Z-pole paper. Compared to the final Z-pole paper, the updated input measurements are:

mass of the top quark from the Tevatron (updated for winter 2008: final Run-I and published and preliminary Run-II results)
mass and width of the W boson from the Tevatron (updated for winter 2008: final Run-I and published and preliminary Run-II results)
mass and width of the W boson from LEP-2 (updated for summer 2006: final results from Aleph, Delphi, L3, Opal, but preliminary combination)

As before, version 6.42 of ZFITTER is used for SM calculations.

Attention:
Since winter 2004, the global SM fits now use only high-Q2 results from LEP, SLC and the Tevatron (together with the hadronic vacuum polarisation). This disentangles the numerical Higgs-mass constraint and limit from the issue of the high chi2 caused by the low-Q2 NuTeV measurement which, however, has only a small influence on the fitted Higgs mass. Based on these high-Q2 analyses, predictions for low-Q2 measurements such as atomic parity violation in cesium (APV), parity violation in Moller scattering (e-e-), and neutrino-nucleon scattering (NuTeV) are derived.

Answers to FAQs on plots presented below:

Only updated plots are collected on this page.
While the measurements of W mass and W width of all four LEP experiments are now final and used in the combination, the LEP combination itself is still preliminary as it uses a preliminary LEP-2 combined estimate for the effect of color reconnection.
For plots showing generic SM predictions in form of arrows or areas, the following parametric variations are used: dal5had = 0.02758(35), alpha_s = 0.118(3), MZ = 91187.5(2.1) MeV, M_top = 172.6(1.4) GeV, M_Higgs = 300+700-186 GeV (lower limit of 114 GeV as given by the direct search). The arrows are pointing in the direction of increasing parameter values!
Higgs constraint from each measurement:
- For each observable, the corresponding constraint on the Higgs mass is determined in a full MSM fit to the measurement result of this observable, constraining dal5had=0.02758+-0.00035, alpha_s=0.118+-0.003, MZ = 91.1875+-0.0021 GeV and M_top=172.6+-1.4 GeV.
- For Higgs masses larger than about 1 TeV, the MSM and its formulae used do not make too much sense, so that part of the Higgs mass regime is cut of as it should not be taken quantitatively.
- The vertical green band denotes the overall constraint on the Higgs mass derived from the fit to all data.
- The vertical black line denotes the limit on the Higgs mass obtained from the direct search at LEP-2.
- The effects of real Higgs-strahlung, Z*+H, is not taken into account, neither in the experimental analyses (such as Higgs-mass dependent efficiencies for various Z*H decay channels) nor in the calculation of MSM predictions (increased Z decay widths). Thus quantitative conclusions from individual observables are uncertain in the low Higgs-mass regime.

Enjoy!