Notes from Nov. 2006 GlueX Software Workshop

1. It was discussed and decided that we should place comment lines that clearly seperate the HDGeant and HDFast portions of the HDDS files rather than discard the HDFast portions altogether. The comment should make it clear that the remaining part of the file does not need to be updated when making changes to the geometry as we no longer officially support HDFast.
2. Geant 4 is actively being developed by Richard Jones and is on track for having a working prototype by the end of 2006.
3. D.L. Remarked that we may need to repeat the CDC/FDC acceptance studies using more hits. The study last summer used 8 hits as a criteria, but efficiency plots indicate significantly more may be needed.
4. HDDS needs to be updated with the latest FDC design which has only 96 sense wires (down from 119). The 1-page summary needs to be updated also to describe this change.
5. BCAL segmentation is still under study. A baseline for this needs to be decided on quickly.
6. HDGeant needs to be updated with the correct BCAL attenuation length of 300cm (currently HDGeant uses 150cm).
7. Reconstruction code needs to be reviewed and fixed. The version in the repository may not be the most recent. This is critical for studying the effect of the FDC cabling on the BCAL resolution in the far downstream region.
8. HDDS needs to be updated with the correct attenuation length for the new UPV design that includes wave-shifting fibers and therefore, much less attenuation. The number should be in the 1-page summary for the UPV.
9. Paul would like more detailed drawings of the upstream end of the GlueX detector. Some were posted to the DocDB very recently as GlueX-doc-725.
10. Paul will study the depth dependence of the energy reconstruction in the UPV due to using different sampling fractions in the front and rear of the detector.
11. The FCAL geometry needs to be updated in HDDS/HDGeant to reflect the recent increase from 2276 to 2800 blocks.
12. The energy resolution of the FCAL in HDGeant needs to be verified.
13. Cherenkov geometry needs to be verified updated in HDDS. The optics does not look quite right. At a minimum, a ring to represent the support structure and the PMTS needs to be added.
14. While some information on the Cherenkov response is being output by HDGeant, there is currently no reconstruction at all for the Cherenkov detector.
15. The Start Counter needs to be updated in HDDS/HDGeant. This can be done with info in Werner's 1-pager.
16. The parametric tagger energy/time generator still needs to be written.

Shower Reconstruction Discussion

The discussion focussed mainly on the need to study the affect of the FDC cabling on the BCAL resolution in the very downstream end where there are cables from 3 of the FDC packages and the incident angle is shallow. We need to determine the resolution as a function of angle once the cables have been described in Geant in some reasonable way.

The need to study the "hole" for photons that skim the downstream corner of the BCAL and are not entirely measured by either the BCAL of the FCAL was restated.

Final Discussion

The discussions on Full Event Reconstruction, what is needed for the Drift Chamber Review, BCAL Readout Review, and CD-2 Review were more or less merged into a single long discussion. Some of the highlights from the first part were:

1. We need to have all "dead" material defined in Geant. Some of this will be density averaged representations.
2. Need a 1-pager on the target and this needs to be put into the simulation.
3. Need to put the CDC 1-pager on the DocDB.
4. Need to move the Cherenkov PMTs to region outside line-of-sight from target to FCAL.
5. Need to compare the number of radiation lengths of air in the beamline to what it would be if replaced by helium bags (with windows).
6. Need to include the support rails in Geant (Elton will give Richard the info on this).

There was a brief discussion of what channel(s) should be simulated and studied in verifying the detector design prior to CD-2. It was suggested that we study the a₂. This would give us good multiplicity final states like:

• a₂ → ρπ → πππ
• a₂ → ηπ → π^oπ^oπ^oπ
• a₂ → ω&piπ → πππππ^o

There was a lot of discussion on the need/benefits of having dE/dx information for PID. Ryan Mitchell's studies on this topic were discussed at length with the final conclusion being that we need to repeat and extend the studies with the current and more complete geometry.

The final part of the discussion was focused on forming a task list of things that need to be completed over the next several months with names and approximate dates. That list is:

1. Alex will repeat and extend Ryan's study of PID with results to be completed by the collaboration meeting in March 2007.
2. Richard will put the more complete Cherenkov description into HDDS/HDGeant at a later time, once we have given the folks at Lebedev a chance to look over and correct the optics. Elton and Alex will contact them through Sergey to see if they are interested/able to do this over the next 2 months.
3. Matt S. will repeat the background rate studies Ryan did, but with the current geometry (including dead material) and with the B-field turned on in the beamline. This will be done by the end of 2006 and will provide background rates as a function of r and z.
4. Richard will implement the updated geometry outlined in the recent 1-pagers into HDGeant by Friday Nov. 17th, 2006.
5. David will implement a working track fitter by Dec. 20th, 2006. This will include the extraction of the "dx" of tracks through tubes and chambers so that dE/dx can be calculated.
6. Determine whether more layers are needed or are possible in the CDC using info provided by Matt S.'s background study. Curtis will do this (though he has yet to be informed) by Jan. 5th, 2007.
7. Study material thickness affect on resolutions in FDC by Jan. 20th, 2007 (Simon and David).
8. Study impact of material on overall photon detection efficiency. This will be done by Mihajlo before the Mar. 2007 collaboration meeting.
9. Study BCAL resolution as impacted by the FDC cabling. This will be done by Univ. Regina group by the Mar. 2007 collab. meeting.
10. First draft of TDR by approx. mid-Feb. 2007. There was some discussion on whether to call this a TDR, but there was general consensus that we need to start working on the next design document. The primary goal by mid-Feb. is to have document in which older information has been weeded out and a clear list of what studies/plots are needed to complete the document.
11. Kinematic fitter will be needed. Initially, just for the π^o, but later for channels that include charged particles. CMU has one that was written for CLAS and was "volunteered" to put it into our repository by the Mar. 2007 collab. meeting.
12. Integration of Tracking and TOF. In general, charged tracks need to be projected to various detector surfaces in the detector (BCAL, TOF, UPV, ...?) in order to match them with hits in those detectors. David will do this by Jan. 31st, 2007.
13. We need to start looking at level-1 trigger simulations again. We will ask Tim Smith if he is interested.
14. Need a good estimate of background rates in the UPV. These can be based on Matt's studies and should be completed by Feb. 2007. (Paul was not present when this was discussed.)

Elton's Notes:

Hi David,

Below are a list of (semi-random) comments and notes that I made during
the software workshop. Perhaps they can be included in any summary you are
producing.

Cheers, Elton.
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FDC:
- need to finalize dimensions of active area of FDC (D=109cm)
- During track fitting what is a reasonable number of hit required per
track.
- Write specifications for FDC: specify goals for position resolution and
need for dE/dx
- Decide on electronics for FDC (FADCs, TDCs)
- Optimization on position of FDC packages
- CDC and FDC - how to include wires into simulation (average material?)
- Get the CLAS12 geometry viewer working for GlueX

CD-2 comments:
- More progress on tracking than on calorimetry. Need work to level the
status of each system.
- PID needs to be revisited, especially with regard to Cerenkov counter
and dE/dx in FDCs

Geometry questions
- Need 1-page target description (elton)
- need to update Cerenkov to move pmts out of active area
- decide on material in/around beamline (air? / He?)
- Suggest geometry for DC rail system.
- Add material to outer shell of CDC to account for additional material
needs (e.g cooling)

- Setup system to make mechanical drawings available to collaboration.
Investigate options using the portal. Need to develop a system which
allows updates and tags "releases"

Mechanical issues to address (Tim?)
- cooling of DC preamps and SiPMs
- alignment of DCs

UPV (Paul)
- How does the segmentation of back layers (with different sampling
fractions) affect energy resolution? (impact on time resolution is likely
small)
- Are FADCs adequate to provide the timing?
- background simulation is required to estimate accidental background
rates in this detector.

Fcal (Matt)
- Fe material cover in front of the Fcal?
- Calibration cover of plexiglass?
-

MC: Identify particle that generates the truth points (Richard)

TOF:
- Hole size is currently 12 cm. This needs to be revisited with new MC
background simulation.