We are unable to directly detect a quark since, almost immediately, it turns into a whole shower (or "jet") of particles which fly off in the direction of the original quark. It is this jet of particles, rather than the original quark, that we observe in our detector.
When a Z0 decays to produce a back-to-back quark-antiquark pair, for example, we therefore expect to see a back-to-back pair of jets in the detector. Most of the particles in these jets are hadrons. We therefore see a number of charged particle tracks and energy deposits in both the electromagnetic and hadronic calorimeters.
Here are a couple of example events.
Note that there may sometimes be a few particles that are produced at a large angle to the two jets. However, these tend to be fairly low momentum particles (as can be seen in this event by the fact they are colour-coded light blue or blue). The high momentum particles tend to be close together in the centre of the jet.
Sometimes a jet may contain an electron or muon as well as hadrons, as is the case in the second example: