Is the picture below a simulation? How to they draw these pictures? The picture is from here.
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This picture is not a simulation, it is an actual collision event. But it could have been either: both real and simulated events can be visualized in this way. Everything is done mainly by using the GEANT4 software package.
(As partially mentioned in the comments, the small boxes are deposits of energy in detectors; different colour for each detector. The lines, both straight and curved, are the reconstructed tracks of particles. And the blue cones are hadronic jets, which are actually spread out.)