Q:

What does 'Truth-level' mean in Particle Physics?

I am sorry to ask an obvious question but I have tried looking this up on Google and cannot get an answer. In particle physics, when it is said that something is 'truth-level', what does that mean?  For example, if someone is referring to a 'truth-level' jet or a plot of jet masses at truth level, could someone explain in layman's terms what this actually means?

A:

Found this proposal:

Define “truth” objects, e.g. stable particles entering the detector, as close as  possible to physics objects reconstructed in the detector

It seems to be an effort to understand detector effects better than up to now.
i.e "true" particles from the interaction vertex hit a detector, and are the source of a number of secondary interactions that are measured in the detector and extrapolated to the true/real  entrant. Example: a true photon hits the electromagnetic calorimeter. A shower of electrons are generated in the detector and measured to extrapolate back at the true one photon entry.

