Animated Z --> mu+ + mu- decay

This is what a typical Z --> mu+ + mu- decay might look like. An electron coming in from the right collides with an anti-electron, a positron, coming in from the left. They annihilate and produce a Z particle, which exists for just a fleeting moment before decaying into one positively and one negatively charged muon.
Muons are charged particles and therefore leave behind a track of ionization in the main tracking detector.

The muons interact very weakly in the calorimeters and they are capable of penetrating the entire detector. The result is that they produce signals in the outermost layer of the detector, the muon detectors. Therefore, if you see signals in the muon detectors, tracks in the tracking detectors, and little activity in the calorimeters, you can be almost sure that the Z has decayed into muons.

In Z decays to muon pairs, the muons are usually the only particles produced.