Summary

• 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

Tag	Features
Y2004	PMD + 3/4 Barrel EMC + 10 ladders of SSD (unmodified) + Option 1
Y2004a	PMD + 3/4 Barrel EMC + 10 ladders of SSD (unmodified) + Option 2
Y2004b	PMD + 3/4 Barrel EMC + 10 ladders of SSD (modified) + Option 2
Y2004x	PMD + 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
Y2005x	PMD + 4/4 Full Barrel EMC + 10 ladders of SSD (modified) + Option 2

Subsystems included

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

Name	Geometry Source File	New/Changed	Usable in Y2004	Contact 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

• 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 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

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).