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Some simplifications have been made, especially detector internal geometries which are important for detector response but not for this application. It is important to maintain the proper isotopic composition of materials as neutron cross sections are sensitive.
Validation against data
Now that there is data from LHC, the calculations can be compared with the measured counting rates in muon detectors. A minimum instantaneous luminosity is necessary so cavern background is not overwhelmed by cosmic rays, electronic noise and so on. Discussions with the muon detector groups lead us to believe that this minimum luminosity is ~ 10^31^ cm^-2^ sec^-1^.
Cavern background files
The calculated background can be added to signal Monte Carlo events to simulate what a real event would look like in the presence of background. We define "scoring volumes" around muon chambers in the FLUGG application, and write out all particles that cross into these scoring volumes. This file of 4-vectors is then used as input in normal ATLAS simulation. Each particle is tracked through ATLAS, depositing energy in the detector like particles from other sources. We add these energy deposits to those from the signal Monte Carlo event, and then simulate the detector's electronic response to this combination of signal plus background.
sLHC Studies
ATLAS will be replacing the Inner Detector tracker for Super LHC. It is expected to be an all-Silicon detector with pixels and strips. We believe additional shielding is needed for the FCAL. It is also expected to replace part of the muon spectrometer detectors. The scope of the muon upgrade has great uncertainty at this time. It can be as little as replacing the endcap detectors at small radii, or it can be replacing all muon detectors, depending on the background level. One of the goals of the cavern background calculation is to provide a more reliable prediction.
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