LEP EW WG Plots for the big LEP-2 Paper

Latest corrections and/or modifications 02-March-2012.

You can find here the plots that have been produced for the big LEP-2 paper (winter 2012/13). The results are all final.

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:

hadronic vacuum polarisation (exp. driven, updated for winter 2011)
mass of the top quark from the Tevatron (updated for summer 2012: final Run-I results and published Run-II results)
mass and width of the W boson from the Tevatron (updated for winter 2012: final Run-I results and published Run-II results)
mass and width of the W boson from LEP-2 (updated for summer 2006: final results from Aleph, Delphi, L3, Opal; final combination March 2011)

Version 6.43 of ZFITTER is used for SM calculations, fixing a small bug w.r.t. 6.42 used previously.

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 = 0.02750(33), alpha_s = 0.118(3), MZ = 91187.5(2.1) MeV, M_top = 173.2(0.9) 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! For plots showing exclusions based on direct searches, the excluded band corresponds to the summer 2012 Tevatron combination (100-103 GeV, 147-180 GeV) and the Summer 2012 LHC exclusion (110-120 GeV, 128-600 GeV).
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=0.02750+-0.00033, alpha_s=0.118+-0.003, MZ = 91.1875+-0.0021 GeV and M_top=173.2+-0.9 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!