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

68 Section 2: CDF Physics Analysis
Figure 33: The pp ! WW cross section measured by CDF at 1:8 TeV compared to theory
predictions.
W + production. Another interesting diboson process is W production. CDF has
measured the cross section of this process using the leptonic decay mode of the W [19], but
no serious eort has been made in the more challenging hadronic channel. Here the data
sample is the high E T photon sample, and the primary backgrounds are + 2 jet production
and fake photons from neutral hadrons. Hall and Dorigo have begun looking at the Run I
data to determine if it is feasible to observe W 's in this sample. If a signal is found its peak
position can be used to set the energy scale for the calorimetry. Also any experience we can
gain with hadronic W decays will be useful in other related analyses.
Trileptons, and Same-Sign Dileptons. The appearance of WW and WZ events in purely
leptonic nal states is interesting, too. Schmitt identied events with three leptons (`trileptons')
or two leptons with the same sign (`same-sign dileptons') as sensitivechannels for higgs
bosons of intermediate mass (M h > 135 GeV). This comes about through pp ! Wh followed
by h ! WW () , which dominates for M h > 135 GeV. If all three W 's decay to leptons,
then a very clean topology results. (This topology has been studied already in the context
of a search for associated chargino and neutralino production.) Schmitt has developed an
eective set of selection criteria. Some examples of his cuts are shown in Fig. 34
A second clean topology arises when the two W 's with the same charge decay leptonically
with the third decaying hadronically. This topology is called the `same-sign dilepton'
topology, and due to the higher rate, is more powerful than the trilepton topology. Schmitt