Muon spectrometer hits are expected to be dominated by background with a small component due to true (high-pT) muons. It is important to understand this background under present conditions and to extrapolate with confidence to design luminosity. We have undertaken a major effort to calculate this background. The results can be confronted with data from the muon spectrometer in the early 2010 running.
We will be using data from all the muon detectors: MDT, RPC, TGC and CSC. In addition, we will use data from the MPX detector. Comparisons will check the counting rates, spatial distributions, etc.