Muons are particles just like electrons, but 200
times heavier. They are the only detectable particles that can
traverse all the calorimeter absorbers without being stopped.
The muon spectrometer surrounds the calorimeter and measures muon
paths to determine their momenta with high precision.
It consists of thousands of charged particle
sensors placed in the magnetic field produced
by large superconducting toroidal coils.
The sensors are similar to the straws described
for the inner detector, but with larger
tube diameters.
