Experiment Proposal - opera - Infn

The isolation cuts makes use of the fact that hadron tracks are usually embedded in a hadronic shower,
while the muon track tends to be more isolated. For each plane one computes the distance between the
hit belonging to the candidate muon track and the position of the centroid of all the other hits. Excluding
the first 3 planes after the vertex, the average of this distance is taken as the first discriminating variable
between muons and hadrons.
The second variable is the number of planes containing no other hits than the one belonging to the
track. Tracks for which the average distance from the plane centroid is larger than 20 cm or the number
of planes on which they are isolated is higher than 6 are identified as muons (Fig. 131).
Figure 131: Effect of the topological cut on events with the longest track longer than 10 hits but not
reaching the end of the spectrometer for ν µ CC and NC events. The events falling in the box are classified
as NC.
The combination of range and topology cuts on the longest track in the event results in the efficiencies
shown in Table 13. These efficiencies are calculated on unbiased samples of events before the application
of any other analysis cut. In the complete analysis, the muon identification efficiencies are generally
higher, because low energy events are rejected by other cuts.
In order to increase the identification efficiency for low momentum muons one can also use a method
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