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Triggers and scalers
When studying efficiencies of rare signal triggers, we want to save considerable computational resources by pre-selecting events according to some basic trigger criteria, avoiding the costly propagation and reconstruction of uninteresting events.
One recent example: the study of J/Psi and Upsilon trigger based on calorimeter hits.
A new feature has been implemented that includes:
- A template for the event selection logic
- Augmented event header structure which carries the running scaler for rejected events, allowing the user to correctly calculate the normalization factors.
- The “g2t” interface with reconstruction for transparent access to such data in root files.
How to do that:
- Write the “AGUDIGI” subroutine called automatically by GEANT at the hits digitization stage
- Use any of the methods available to check for the trigger condition such as number of hits in a particular detector subsystem
- Set the IEOTRI flag (standard GEANT) according to the event selection criteria. Rejected events will then be completely ignored and won’t be present in the output stream.