A single atmospheric muon event. The thin outer cylinder is the Time Of Flight detector (1) The large inner cylinder is the Time Projection Chamber (2) and the smaller cylinder at the centre isthe silicon Inner Tracking System (3). Muons are reconstructed as two TPC tracks, one in the upper half oft he detector ($up$ track) and the other in the lower half ($down$ track), which are then joined to create a single muon track.