Electroweak measurements from CDF and D0 Page: 4 of 7
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ELECTROWEAK MEASUREMENTS FROM CDF AND DO
Physics Department, University of California at Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90024, USA
FOR THE CDF AND DO COLLABORATIONS
This paper highlights results from electroweak measurements recently obtained by the CDF and DO
collaborations in 1.8 TeV pp collisions. The W decay width was extracted from the measurement of W/Z
cross section times leptonic branching ratios, and in a direct measurement from a fit of the high-mass tail
of the transverse mass spectrum of the W system. Various limits on anomalous gauge boson couplings
were obtained in studies of W/Z + y processes, single leptonic WW, WZ production and double leptonic
WW production. Values for aB(Wy -+ Airy), aB(Zy - 1+-y), and a(pp -+ WW +X) were measured.
CDF also reports on the observation of an asymmetry in photon rapidity distributions as predicted by
the Standard Model.
Experiments at the CERN LEP e+e- collider have col-
lected large samples of Z bosons and have measured its
properties with great accuracy. On the other hand, large
amounts of W bosons are presently available only at
the Tevatron pp collider at Fermilab, which thus offers
a unique opportunity to make precision measurements
in electroweak physics and to test the Standard Model
(SM) in the 1 TeV range.
During the 1992-93 Tevatron collider run ('Run la'),
the CDF and DO experiments recorded ~ 20 pb-1 and
13 pb-1 of data, respectively.
In the following, a summary of electroweak results
obtained by CDF and DO by analyzing Run la data will
be given. Topics are the measurements of the W width,
vector boson self-couplings and cross sections. The W
mass measurement is described in a parallel contribution
to these proceedings by L. Nodulman.
In addition, recent, preliminary data from the ongo-
ing Tevatron run ('Run ib'), which started in late 1993,
will be presented. Preliminary results are marked by a
dagger t throughout this paper.
2 W, Z Identification
The W and Z boson selection criteria are similar in the
various analyses presented in this paper. Both exper-
iments require an isolated electron or muon with high
transverse momentum. In W events, the missing trans-
verse energy, $P, must be greater than 20 GeV. Z events
are defined by the occurence of a second lepton which-
with the first lepton-forms an invariant mass close to
the Z mass. Specific event quality cuts can be found in
the references for each analysis.
3 Measurement of the Inclusive W and Z Cross
From a precise measurement of the number of clean W/Z
events and their backgrounds (multijets, tauonic W/Z
decays, Z events misidentified as W bosons) in the Run
la data samples, and a detailed study of efficiencies and
detector acceptances, D0 and CDF extracted the inclu-
sive cross sections aB(W -+ Lv) and aB(Z -+ +f-) in
the electron and muon channels1-2.
The results for the cross sections and their ratios,
R = aB(W -+ v)/aB(Z - f-+-), are compared to the
SM predictions in Tab. 1. The integrated luminosity, C,
of the electron (e) and muon (p) data sets is for CDF
19.6 + 0.7 pb-1 (e) and 18.8 + 0.7 pb-1(p), and for DO
12.8 + 0.7 pb-1 (e) and 11.4 + 0.6 pb-1(p). Additionally,
we list preliminary DO results from Run lb (C = 25.1 +
1.4 pb-1 (e) and 30.7+ 1.7 pb-1(p) ).
4 Measurement of the Width of the W Boson
The W width is determined indirectly through the mea-
surement of the ratios of the W/Z production cross sec-
tion times branching ratio into leptons2, given by
R - aB(W -+ v)
aB(Z - f-)
_aw ,(W-* v) ,(Z)
OZ ,( Z - f-) ( W)
CDF uses electron data only; DO makes use of the com-
bined electron + muon decay channel.
The predicted ratio of the production cross sec-
tions for W and Z bosons in pp collisions, aw/az, is
calculated3 to be 3.33 + 0.03. For the remaining quanti-
ties, CDF and DO chose slightly different input parame-
ters. CDF uses the individual LEP measurements of the
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Neuberger, D. & Collaborations, CDF and D0. Electroweak measurements from CDF and D0, report, July 1, 1996; Batavia, Illinois. (digital.library.unt.edu/ark:/67531/metadc676626/m1/4/: accessed December 13, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.