Questions and answers: detectors

1. What are the two types of tracking detectors, and what is the difference between them?
   The two types are semiconductors and wire chambers. In a wire chamber the particles are detected when they collide with atoms in the gas in the wire chamber. The collisions knock out electrons from the atoms. The free electrons moves to an anode (+) and the ions to a cathode (-). In a semiconducting detector the particles instead collide with atoms in the semiconducting material. This will create electron-hole-pairs that are detected at the electrodes.
2. Why are the tracking detectors placed inside the calorimeters?
   Because the calorimeters destroy the original particles in the process of creating showers of secondary particles, it is then impossible to decide the trajectory of the original particle.
3. What quantity does a calorimeter measure?
   Calorimeters measure the energy of the particles.
4. Why are the muon detectors placed furthest out?
   Since the muon are the only particle (except neutrinos) that can penetrate the inner layers of detectors.
5. How can we now that neutrinos are created when they are undetectable?
   One can assume that neutrinos were created if the energy or the momentum before the collision is not the same as after it.