StEvent - what’s that ?
StEvent is the name of the STAR data model.
It consist of a set of ~80 classes.
- Classes represent tracks, hits, vertices, PID info, etc.
- Smaller objects are collected in so called containers (or collections)
- Classes are linked (by reference or pointer) together which allows easy navigation. E.g. one can navigate from a track to the individual hits assigned to the track.
- At the top there’s a class from which you can access all objects stored. This class is called StEvent.
To do analysis on the DST level you need a pointer or reference to the top class StEvent. At the beginning of StAnalysisMaker::Make() you therefore find:
event = (StEvent *) GetInputDS("StEvent");
if (!event) … // bad, no event