STAR  Computing  Simulation  
The Current STAR Geometry


The STAR detector hardware has undergone incremental changes between the runs conducted in 2003 and 2004. This included:
  • Augmented silicon strip detector (SSD) configuration (10 ladders located at specific angles). Further, there was an addtional version of the SSD code that included additional structural elements and hence more material in the geometry model. See table below.
  • Augmented Barrel TOF detector configuration (to be documented separately).
  • Additional modules in the barrel EMC, covering a half of the East half-barrel. Now there are 60 modules in the West part, and 30 in the East.
  • Additional sectors in the endcap EMC (west), completing the "wheel"
  • The Photon Multiplicity Detector (PMD)

As was announced a while ago, the Silicon Strip detector geometry code has been factored out of the Silicon Vertex Detector (the SVT) and is now a separately maintained file.

The geometry of the Zero Degree Calorimeter will not be 100% correctly represented in Y2004, as stated by Aihong. This is not of much concern because (a) it's likely to require custom simulation run anyway, because of its extreme position in the STAR detector (b) it won't affect the background, in the rest of the STAR detector elements, again, because of its position

The Forward Pion Detector will have the most recent geometry description in Y2004, however according to Akio their group is not planning on using the results from this detector in the upcoming wave of simulation. An interesting fact is that the simulation of Cherenkov photons can be prohibitively expensive, according to Akio. This is worth checking in a realistic setup.

Missing in 2003 and in most of the Y2004 simulations was the model of the FTPC Readout Electronics cage, termed FTRO in our model. This was included in the last cut of the 2004 geometry and in all of the 2005 cuts (table below).

The base geometry tag for this configuration is called Y2004. Subsequent corrected and otherwise modified versions are labeled Y2004A,Y2004B etc. The tag Y2004X is reserved for a geometry similar to Y2004B but with a full barrel calorimeter. This is a convention similar we used in 2003 and shall continue using in 2005.

Note that all of the below contains 1 Full Endcap EMC. "Option 1" means low thresholds for the electromagnetic processes simulation in PMD, whereas "Option 2" is standard thresholds for the electromagnetic processes simulation

Y2004 PMD + 3/4 Barrel EMC + 10 ladders of SSD (unmodified) + Option 1
Y2004aPMD + 3/4 Barrel EMC + 10 ladders of SSD (unmodified) + Option 2
Y2004bPMD + 3/4 Barrel EMC + 10 ladders of SSD (modified) + Option 2
Y2004xPMD + 4/4 Full Barrel EMC + 10 ladders of SSD (unmodified)+ Option 2
Y2005 PMD + 3/4 Barrel EMC + 10 ladders of SSD (modified) + Option 2
Y2005xPMD + 4/4 Full Barrel EMC + 10 ladders of SSD (modified) + Option 2

Subsystems included

If you are interested in the technical documentation about individual subsystems in STAR, it can be found here.

For quick reference, here is a list of subsystems included in the year 2004 geometry definition, their respective source files, status and contact persons.

NameGeometry Source FileNew/ChangedUsable in Y2004Contact person(s)
Beam Beam counter bbcmgeo.g  + Akio Ogawa
Barrel Calorimeter calbgeo.g + + Alexei Pavlinov
Endcap Calorimeter ecalgeo.g + + Jan Balewski
Zero Degree Calorimeter zcalgeo.g +  Aihong Tang
Forward Pion Detector fpdmgeo.g   Akio Ogawa
Photon Multiplicity Detector phmdgeo.g + + Subhasis Chattopadhyay, Dipak Mishra
Vertex Position Detector vpddgeo.g + + Frank Geurts, Bill Llope
Silicon Strip Detector sisdgeo.g + + Christelle Roy
Silicon Vertex Detector svttgeo3.g  + Helen Caines
Barrel TOF Detector btofgeo2.g + + Frank Geurts, Bill Llope
TPC tpcegeo.g  +  
Forward TPC (FTPC) ftpcgeo.g  + Janet Seyboth
FTPC support structure supogeo.g  + Maxim Potekhin
FTPC Readout Electronics ftrogeo.g  + Tapan Nayak
Beam Pipe pipegeo.g  + Bill Christie

The Y2004 configuration of the Barrel Time-of-Flight system

The following is an exerpt from the "MC Geometry page" in the production area:

  • TOF: two trays, TOFp (at new location) and TOFr, on the east side
  • TOFp tray in East Barrel at the position 33, covers about 1 unit of pseudorapidity and ~1/60th of the azimuth
  • TOFr tray in East Barrel at the position 23, new construction, the 2nd generation prototype, covers in total ~30-40% of a unit of pseudorapidity and ~1/60th of the azimuth

Appendix I: The FTPC readout electronics cage

The FTPC readout electronics is suppported by, and housed in a cylindrical cage-like structure comprising 5 identical sectors. It is formed by flanges on either end of the sylinder connected by stuts running lengthwise, with PCB's mounted in between. Here is a recent picture of the assembly:

The material present in this structure affects the response of the Photon Multiplicity Detector located downstream, and whose acceptance is largely covered by the projection of the FTPC readout. It is important therefor to include this structure into the STAR Geant simulation.

The first cut of the geometry has been made and added to the code base as the directory "ftro", for "FTPC readout". Further developement will be done by Maxim Potekhin and Tapan Nayak, who's representing the PHMD group, and a member of the FTPC team TBA. This is the graphic of the existing model which includes main aluminum structures and PCBs:

Appendix II: The IST and FST Detectors

The IST and FST stand for Inner STAR Tracker and Forward STAR Tracker, correspondingly. At the time of this writing (December 2004) these are upgrade projects in preliminary stages of planning and simulation.

A separate document by Gerrit van Nieuwenhuizen describes the layout of the proposed detectors.

Currently, we have a geometry tag IST1 that's an experimental one, i.e. it doesn't receive production support. It is used to model and investigate the preliminary versions of the two detectors. Once activated, it would cause the STAR Geant geometry to contain these two systems (please refer to the link above).

Last updated by Maxim Potekhin on 12/06/2004