Searches for excited and new leptons and quarks at the Tevatron Page: 3 of 4
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November 2, 2006 11:58 WSPC/Trim Size: lOin x 7in for Proceedingsi
3
ber of different signatures, CDF has concen-
trated on a few signatures that are promising
for discovering non-Standard Model physics
(signature-based searches). In this talk, we
report results for two such signatures:
* High PT Z's.
* High mass dileptons (CC, pp, Cp).
For concreteness, these searches are inter-
preted in terms of the BPT model of new
quarks described above.2
4.1. High PT Z Search
For this search, event selection consists of
two opposite sign high-PT leptons (cc or pp)
consistent with the Z boson mass, with final
selection based on the PT of the lepton pair.
The major background is Standard Model
Z+jets production. The integrated luminos-
ity is 305 pb-1. Figure 3 shows a comparison
of observed and expected background events
as a function of pTZ. No excess above ex-
pected background is observed.
This negative result can be expressed
in a model-independent fashion as an upper
limit on the anomalous Z boson differential
cross section du/dpTz. The result is shown
in Fig. 4. In terms of BPT model quarks,
CDF sets an upper limit on the production
cross section of UQQ < 0.35 pb for mQ 300
GeV (95% CL).
4.2. High Mass Dilepton Search
For this search, the basic signature is two
high PT isolated leptons (cp or like-sign cc,
pp), plus at least two jets with ET > 50 GeV,
and HT > 400 GeV (HT is the sum of the
ET of jets and leptons). The main physics
backgrounds are top and diboson production.
The integrated luminosity used in this search
is 929 pb-1. A comparison of data and ex-
pected background vs. HT in the ep chan-
nel, before the jet requirement, is shown in
Fig. 5. After the jet requirement, two events
remain in data with an expected background--DA TA-
10
y 1 - tt f e'e. -
d1o' - -
0 50 100 150 200 250 300 350 400
P GeV
10 zZ
S-
-.,Z- <t<
10, -
0 50 100 150 200 250 300 350 400
PGeV
Fig. 3. Observed and expected events vs. pTZ for
electrons (top) muons (bottom).
of 1.9 0.2 events. For the like-sign cc and pp
channels, no data events pass all cuts, with
an expected background of 0.9 0.09 events.
There is no evidence of non-Standard Model
events. This negative result has been used to
set an upper limit on the production of 300
GeV BPT quarks of UQQ < 0.40 pb (90%
CL).
5. Summary and Prospects
In this talk, results of several searches for
non-Standard Model fermions have been pre-
sented. No evidence for non-Standard Model
physics is seen. Several model-independent
and model-dependent limits have been set on
nonstandard particles and processes.
Several of the analyses shown here are
based on a fraction of the full Run Ha inte-
grated luminosity (about 1 fb-1). Updated
results based on the full Run Ha datasetichep06'proceeding
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Greenlee, H.B. Searches for excited and new leptons and quarks at the Tevatron, article, July 1, 2006; Batavia, Illinois. (https://digital.library.unt.edu/ark:/67531/metadc893848/m1/3/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.