trgEM (Neil Dyce) October 1996
Overview
This document outlines the current state of the calorimeter trigger simulation program trgEM. trgEM is a FORTRAN 77 package to simulate the L1 calorimeter trigger. It is interfaced to the reconstruction framework via the trgFrame package. It originally
operated in a stand-alone mode.
Works on GEANT hit data, usually now directly from xdr files through trgFrame. Hit mixing for background studies is performed in trgFrame.
The Calorimeter trigger
An overview of the calorimeter trigger system is shown above (click for postscript). The simulation corresponds to the latest engineering design for the Trigger workshop of October 1996.
The input to the trigger is 280 tower energies, formed from blocks of 24 crystal by the calorimeter DAQ. In the trigger the tower energies are summed into phi strips. To contain showers, the strip sum from the next higher phi strip is added in
clustering. Feature extraction is then performed on the strip clusters, and three energy thresholds are used to form trigger objects. In addition tower energies from the rear of the barrel (for wide angle Bhabhas) and forward endcap can be used in the
trigger, but these are not feature extracted.
Design considerations
The design of the calorimeter trigger simulation is driven by the need to study backgrounds, and the long lifetime of the signals from the detector compared to the beam crossing interval. Because signals from several events may be present at any one time
the hit mixing, now performed in trgFrame, is essential for calorimeter trigger studies. A time history of the overlaid events can then be constructed before data are passed through the trigger simulation.
The program has evolved in tandem with the electronics design as possible algorithms and configurations have been considered. In the future the calorimeter trigger simulation will continue to closely simulate of the actual hardware, as it is finalised.
It will stay integrated with the reconstruction framework.
Implementation
trgEM is currently implemented as a Fortran77 library of routines which are called from the trigger Framework job trgFrame.
An outline of the program structure is shown below
trgEMFwkBJ (Called from Framework begin Job)
trgEM_Read (dbin)
trgEMSetUp (General initialisation)
trgEMUSStart (User start of run hook)
trgEMFwkEvt (Called from Framework event)
trgEMFwkEvLd (Transfer data from Framework/dbio commons to trgEM's)
trgEMDigi (digitisation)
trgEMTrigger (EM trigger algorithms)
trgEMUSEvent (User event hook called from trgGLTrigger)
trgEMFwkEvt (Called from Framework end job)
trgEMEnd (End of Job stuff)
trgEMUSEnd (User end of job hook)
Runtime control for trgEM is provided for with a dbin file which contains tunable parameters for the signals and electronics as well as the trigger configuration.
Functions
Geometry: The program needs to know the number of theta and phi crystals in order to build trigger towers. Since these numbers are quite stable, they have been hard coded for the trgFrame mode. The stand-alone mode reads them from an ASCII file.
Digitisation: Until recently digitisations of the calorimeter data have not been available from any other source and so a digitised history of the ADC output for each channel is produced internally. It is not intended to permanently store (i.e.
disk or tape) this large amount of data.
Trigger logic: The various proposed trigger algorithms are implemented, both in terms of feature extraction and trigger topology.
Contains about 5,000 lines of F77 code. Programmability is provided by dbin switches.
Last tested with SRT release 1.2.2.
Plans
In the longer term, it is intended to make a objected oriented C++ trigger package to replace trgEM. This will use the recently available digitisation code from the Calorimeter group (EmcSim) and so will be a trigger-specific simulation only.
Manpower
Neil Dyce, package coordinator, developer and user
Paul Dauncey, developer and user
John C. Andress, future developer and user (new Bristol student)
Needs from other parts of simulation
None outside of the trigger simulation.
SRT integration
Available in SRT release 1.2.2. Independent of BBSIM. |
