SVT Third Level Trigger

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Rene Bellwied, Wayne State University February 13, 1995

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Summary of present trigger considerations by SVT group (January 95)

The SVT considers presently only options for the 3rd and 4th level of the STAR trigger system. Fast signal readout does not seem practical for our device. Various triggers are being considered for the 3rd level. In the following I will try to describe these triggers and their effect on STAR. Comparisons to alternate triggers formed by other STAR detectors are drawn. After the trigger descriptions I will comment on the availability of the required code.

L3 Trigger Options

DCC Trigger
- Description: energy loss from inner Si layer per event. enhancement beyond statistical fluctuation might reveal increase in multiplicity and decrease in .
- Modules Needed: energy sum module
- Alternate Trigger: EMC+CTB
Entropy Trigger
- Description: calculate of all charged particles. might be used as measure of rapid entropy increase event by event.
- Modules Needed:
  - SVT tracking
  - SVT momentum reconstruction
- Alternate Trigger:
  - TPC trigger (same functionality)
  - TOF trigger (different coverage, but faster)
Cascade Trigger
- Description: charged particle mulitplicity. Can be deduced from number of hits per layer.
- Modules Needed: SVT cluster finder
- alternate trigger:
  - TPC trigger (same functionality)
  - CTB trigger (less granularity, but faster)
  - EMC trigger (faster and complementary - Et vs. N)
Fluctuation/anysotropy Trigger
- Description: charged particle multiplicity as function of pseudorapidity and azimuth.
- Modules Needed: SVT cluster finder, level algorithm
- Alternate Trigger:
  - TPC trigger (same functionality)
  - CTB trigger (less granularity, but faster)
DCC Tracking Trigger
- Description:charged particle multiplicity as function of pt.
- Modules Needed:
  - SVT cluster finder
  - SVT tracking
- Alternate Trigger:TPC trigger (less coverage in low pt)

Availability of Possible SVT Trigger Algorithms

On I-960
- Algorithm: SVT fast cluster finder (TPC like)
- Contact Person: Michi Botlo, Vladimir Rykov
- Generates: energy sum, x,y-position, moments
On Alpha
- Algorithm: SVT waveform analysis, fast Gaussian
- Contact Person: Dave Read
- Algorithm: SVT tracking, momentum reconstruction
- Contact Person: Claude Pruneau, Ken Wilson, Duncan Prindle
- Algorithm: SVT de/dx, PID module
- Contact Person: Stathes Paganis

All the software listed above (except the fast cluster finder from Michi) exists only in (slow) TAS modules. These modules have to be stripped of their TAS structure and then bench marked on the prototype ALPHA board at UT. The cluster finder can be tested with the CYCLONE board. The focus of the ALPHA tests should be on the level 3 algorithms.