2 The CDF Experiment at Fermilab Contents - Harvard University ...

Section 2: Di-Boson Production 67
1. pp ! WZ with Z !
2. ~t or ~ b pair production
3. pp ! Zh with h ! bb and Z !
4. pp ! qq with one hard parton going o into so-called \extra" dimensions
In some cases a b-tag is called for { but not in all. A sample of events with two jets and
missing energy is clearly related to the sample studied by Spiropulu & Huth in the Run I
data, but is not the same and could contain dierence signals for New Physics. Still, the
experience and in-depth understanding gained from the Run I analysis will prove invaluable
for studies of this sample.
In the following two sections we describe our plans for these studies in the context of
di-boson production and a study of 6E T + jets.
2.4.2 Di-Boson Production
(Prof. Franklin, Prof. Schmitt, Dr. Burkett, Dr. Dorigo, Mr. Hall & Ms. Madrak)
WW production. Madrak, Dorigo and Franklin have begun investigating the isolation
of a WW signal in Run II, starting, of course, with Run I data. The cross section is about
10 pb. An observation of W + W , pairs was reported by CDF in 1996 [18], using the double
leptonic topology (see Fig. 33). Although an event sample with two high P T leptons and
large 6E T is very clean, this nal state suers from a small rate due to the square of the
branching ratio Br(W ! e; ). The nal state involving one hadronic and one leptonic
W decay has never been observed at a hadron collider: the main hindrance is the irreducible
background from single W production and two jets from gluon radiation in the initial state.
This background is larger by roughly two orders of magnitude.
We think it may be possible to extract some evidence for the WW ! `jj signal in
Run I data by selecting events with a high P T lepton, 6E T , and two jets. We may study
the dijet mass spectrum after the application of kinematical selection requirements aimed at
dierentiating the QCD radiation processes from the weak W decay. The tagging of charm
jets may also constitute a useful tool to reduce the background. If we nd no signal in Run I
we can still look forward to rening and optimizing our analysis strategy, in order to be
ready to observe a clear peak with Run II data.