Notes from Nov. 2006 GlueX Software Workshop
- 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.
- Geant 4 is actively being developed by Richard Jones and is on
track for having a working prototype by the end of 2006.
- 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
- 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.
- BCAL segmentation is still under study. A baseline for this
needs to be decided on quickly.
- HDGeant needs to be updated with the correct BCAL attenuation
length of 300cm (currently HDGeant uses 150cm).
- 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.
- 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.
- Paul would like more detailed drawings of the upstream end of
the GlueX detector. Some were posted to the DocDB very recently
- 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.
- The FCAL geometry needs to be updated in HDDS/HDGeant to reflect
the recent increase from 2276 to 2800 blocks.
- The energy resolution of the FCAL in HDGeant needs to be verified.
- 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
- While some information on
the Cherenkov response is being output by HDGeant, there is
currently no reconstruction at all for the Cherenkov detector.
- The Start Counter needs to be updated in HDDS/HDGeant.
This can be done with info in Werner's 1-pager.
- The parametric tagger energy/time generator still needs to
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.
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:
- We need to have all "dead" material defined in Geant. Some
of this will be density averaged representations.
- Need a 1-pager on the target and this needs to be put into
- Need to put the CDC 1-pager on the DocDB.
- Need to move the Cherenkov PMTs to region outside
line-of-sight from target to FCAL.
- 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).
- 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:
From which we could reconstruct sharp resonances like the
ρ and η from charged tracks and photons respectively.
- a2 → ρπ → πππ
- a2 → ηπ → πoπoπoπ
- a2 → ω&piπ → πππππo
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:
- Alex will repeat and extend Ryan's study of PID with results
to be completed by the collaboration meeting in March 2007.
- 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.
- 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.
- Richard will implement the updated geometry outlined in the
recent 1-pagers into HDGeant by Friday Nov. 17th, 2006.
- 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.
- 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.
- Study material thickness affect on resolutions in FDC
by Jan. 20th, 2007 (Simon and David).
- Study impact of material on overall photon detection efficiency.
This will be done by Mihajlo before the Mar. 2007 collaboration
- Study BCAL resolution as impacted by the FDC cabling. This will
be done by Univ. Regina group by the Mar. 2007 collab. meeting.
- 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.
- Kinematic fitter will be needed. Initially, just for the πo,
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.
- 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.
- We need to start looking at level-1 trigger simulations again.
We will ask Tim Smith if he is interested.
- 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.)