Abstract
This paper reviews our current understanding of the effects of radiative corrections on the experimental measurements which will be made at the SLC and at LEP. It discusses how the shape of the Z0 resonance is modified by initial state radiation, and considers how the Z0 self energy corrections allow a probe of physics above the Z0 mass scale. In particular, the sensitivity to the top quark mass of the various asymmetry measurements which may be made at the Z0 pole is discussed.
Work supported by the Department of Energy, contract DE-0286ER-40253.
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References
When the top mass is measured we could instead adjust the Higgs mass or the Higgs structure of the model.
This interpretation assumes that no unknown particles are contributing to the running.
“A Precision Measurement of the Mass and Width of the Z0 Resonance at the Fermilab Tevatron”,CDF Collaboration, PRL63, 720(1989); “Measurements of Z0 Boson Resonance Parameters in e+e- Annihilation”, M2 Collaboration, PRL63, 2173(1989); “Determination of the Number of Light Neutrino Species”, ALEPH Collaboration, CERN-EP/89–132; “Measurement of the Mass and Width of the Z0 Particle from Multihadronic Final States Produced in e+e- Annihilations”, DELPHI Collaboration,CERN-EP/89–134; “A Determination of the Properties of the Neutral Intermediate Vector Boson Z0”, L3 collaboration, L3 preprint/001; “Measurement of the Z0 Mass and Width with the OPAL detector at LEP”, OPAL collaboration, CERN-EP/89–133.
The β parameter can be traced back to a paper by M.Greco in PL 56B,367 (1975). The value of the parameter at the low energies the calculations were then being applied at was 0.007, and since the James Bond movies were popular the name β was chosen.
Detailed formulae describing these effects can be found in R.N. Cahn, “Analytic forms for the e+e- annihilation cross-section near the Z0 including initial state radiation”, Phys.Rev. D36:2666,1987.
Another useful treatment can be found in D.Y. Bardin et al,” Energy dependent width effects in Z0 line shape”, Phys.Lett. B206:539,1988. An apparent disagreement as to the size of the energy dependent width effect between these two treatments can be traced to a difference in the form they assume for the Breit-Wigner when the width is constant. See also the “Z line Shape” by D.Y. Bardin et al. in the second CERN yellow report on LEP Z0 physics, this contains an exhaustive list of references.
For more details see W.Beenakker et al, “Rules of thumb for the Z0 line shape”, University of Leiden preprint, October 1989.
One may or may not be free to choose all three of these variables. Various assumptions may be made which allow the width and/or the cross-section to be calculated within the framework of the Standard Model.
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As of July 1989 the differences between the different libraries of routines to calculate electroweak corrections (Hollik, Stuart) were being resolved, and a standard library was coming into existence. A note of caution should however be sounded: agreement over results when particular terms are included is not the same as including the effects of all diagrams which contribute.
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Further experiments at low energies could reduce this error significantly.
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When the W mass is much better measured we can use it to predict the top mass, or vice versa. The current uncertainty in the W mass is too large for interesting limits on the top mass to be obtained.
This comparison, and that of table 5 uses the versions of code supplied by W.Hollik and B.Lynn to the author. They do not rely on previously published values. The small difference can be attributed to slightly different treatments by the two authors of b/t quark effects.
There was some discussion at the conference about the gauge invariance of some of the running coupling schemes, in particular the sin2 *θ scheme. The problems raised with the original formulation of this scheme (D. Kennedy and B. W. Lynn, Nucl. Phys. B322:l,1989.) have been addressed by Lynn in SU-ITP-867 (Aug 1989) which has been submitted to Phys.Lett. Similar calculations have been developed by W. Hollik, the interested reader is recommended to read his DESY report 88–188, for a complete discussion of this issue.
Sin2θw is decreased by a similar amount. The direction of the change is different than one might expect because increasing the Z0 mass by 45 MeV/c2 corresponds to an increase of 50 MeV/c2 in the W mass if everything else is kept fixed.
Increasing the Higgs mass to 1000 GeV would raise sin2 * θ. Calculations give 0.0236, but they are unreliable for such a high Higgs mass.
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© 1990 Plenum Press, New York
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Rankin, P. (1990). Radiative Corrections — An Experimentalist’s View. In: Dombey, N., Boudjema, F. (eds) Radiative Corrections. NATO ASI Series, vol 233. Springer, Boston, MA. https://doi.org/10.1007/978-1-4684-9054-1_17
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DOI: https://doi.org/10.1007/978-1-4684-9054-1_17
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