Study of vector boson decay and determination of the Standard Model parameters at hadronic colliders Page: 3 of 27
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With the advent of high energy colliders and the production of on-shell vector
bosons, we have the prospect of measuring the Standard Model parameters unhindered
by the ambiguities that have plagued measurements at lower energy.
The most precise collider result to date is the the value of the Z mass derived from
resonance parameters in e+e- annihilation. At hadron colliders, vector bosons are
observed only in their final state, and the precision of a mass measurement is limited
by the uncertainty in the absolute detector calibration. This disadvantage is somewhat
counterbalanced, however, by the copious sample of W bosons produced along with the
Z in hadronic collisons. This well stocked electroweak laboratory has several utilities:
1. When higher order corrections are included, the solution to the theory requires, in
addition to the Z mass, one other constraint, which could be the W mass, or sin2 #w,
or M|0p. Measurement of both masses allows calculation of the other two variables.
2. The electroweak mixing parameter, sin2 0w, is a function of Mw/M7, and the ex-
perimental mass scale error cancels in the ratio.
3. Sin2 &vf can also be measured via the front-back asymmetry in the decay lepton
angular distribution, providing, in effect, a second completely different measurement
method in the same experiment.
4. The LEP/SLC Z mass can be used to understand the detector mass scale error in
the measurement of Mz, enhancing the ultimate precision in the measurement Mw.
I will begin this report with a experimenter’s exegisis of the issues surrounding the
determination of the Standard Model parameters. I then turn to the measurment of Mz
and Mw nt CDF and UA2, following Refs. 2, 3, and 4. I pay close attention to calibration
issues, and will attempt to demonstrate that the power of the detectors, coupled with the
richness of the data, provides in situ laboratories for understanding even the thorniest
of systematic effects. I follow this with a discussion of a very different approach, the
measurement of sin2 #w from the charge asymmetry in Z decay.
In all cases, I focus on the most precise values as derived from the recent work by
CDF and UA2. For an excellent review of the situation up to 1988, see the lectures of
DiLella at the 1988 Cargese Summer School.
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Amidei, D. Study of vector boson decay and determination of the Standard Model parameters at hadronic colliders, article, January 11, 1991; Batavia, Illinois. (https://digital.library.unt.edu/ark:/67531/metadc1100190/m1/3/: accessed March 21, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.