Model Independent Search for Deviations from the Standard Model ...

3.2. Concept 33
cal problem as many QCD processes must be simulated and an enormous number of
events must be generated to develop a proper background sample (see Section 6.2).
As a result, the analysis presented here extracts the QCD-background from the data.
Another disadvantage of MIS is that one does not expect a certain specied signal,
so the selection cuts cannot be optimized. This restricts the sensitivity of MIS to
relatively large deviations from SM. SUSY-signals with small cross sections cannot
be observed. Here it is important to note that MIS is only an alternative form of
analysis. Many other analyses attend to these small signals; it is not the task of MIS
to cover all needs.
Related to the absence of a signal is the fact that MIS cannot set any limits. Only
the level of consistency between observed data and the MC models can be quantied
such that regions of signicant deviation can be identied. Also, the interpretation
of these deviations is not trivial, as it is dicult to relate an observed deviation
to a specic extension of the SM. The idea of MIS is to identify these regions and
then start to rene the analysis by sacricing model independence. Finding denite
explanations for a deviations is often a separate step and a seperate analysis.
± Finally, one should mention that it is a chance as well as an obstacle that a Model
Independent Analysis has received rather limited attention so far. There are only a
few articles and papers providing information and guidelines on MIS (see [18], [19]
and [20]). It is an interesting idea where the benets are dicult to estimate, but
the lack of broad experience with MIS presents many possible problems.