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

46 Section 2: CDF Physics Analysis
Indirect Lepton Veto
Since all the Standard Model backgrounds contain in the nal state along with 6E T and
jets also a lepton we dene an isolated track criterion to select the remaining standard model
processes in the data. The composition of the complementary sample of events that do not
contain such an isolated charged track is expected to be QCD events with large 6E T arising
from pure jet calorimeter resolution. Any excess of events in this sample will be the signal
candidates.
We are modelling the QCD background using large monte carlo statistics samples of
inclusive 3 jet QCD events and by varying the jet resolution functions in order to get the
shape variation of the 6E T tails. This is a critical part into arriving to the result of the search
for the supersymmetric signal. Completion of this part of the analysis and optimization of
the requirements for identication of signal candidates will allow us to compare the data with
the total background predictions. The QCD prediction of the low 6E T spectrum for events
with at least three jets compared with the data is shown in gure 24. The comparison of
the sample of events that do contain an isolated track with Standard Model predictions for
the backdrounds mentioned above (where we expect very low or none QCD contribution) is
shown in g 25.
We still need to study and estimate the systematic uncertainties for the Standard Model
predictions. We expect a result of this search by the Fall of 1999.