How are collision events interpreted?

[chaszz]

We see collision detector images showing a lot of curved lines radiating out more or less from the central area. We hear that literally thousands of scientists the world over process and resolve these images and get information from them. How is this done? How can the mass of a particle be determined? How can a specific particle and/or its predecessor and successor particles be identified from these lines, as opposed to all the other particles it might be?

 

[Einj]

The topic you proposed is a really complicated one! Let's talk for example of the identification of a particular kind of particle among all the others. The main feature is that different particles have different propeties (if not they wouldn't be different particles!). The aim of experimental physics is to use our knowledge on this differences to identify different particles. For example, when you see an image from LHC you can see a great number of tracks, which can go straight head from the center of the reaction or can be curved. In LHC deterctor there is a great magnetic field. Charged particles are curved by this field while uncharged particles are not. So curved trajectories means a charged particle, straight trajectories means neautral particles.
This is the main idea. Using different particles proprieties you can identify different particles. For example electrons are charged particles (they are curved) which release all their energy in the electromagnetic calorimeter and then they are stopped. A muon is a charged particle that release a few energy in the electromagnetic calorimeter and that go head so it can be seen also at the extern of this calorimeter. And so on...

On the other hand the ability to predict which particle come from another or which particle produce another is the aim of theoretical physics. And it needs to develope a mathematical model that permits to have prediction.