GlueX Software Meeting minutes

[David Lawrence <davidl@jlab.org>]

Hi All,

    Here are the minutes from yesterday's GlueX Software meeting.

Regards,
-David


==Minutes==

Attendees: David L. (chair), Elton S., Elke A., Curtis M., Eugene C., 
Simon T. , Elliott W.

On the phone/VRVS: Mihajlo K., Matt S., Beni, Oojin K., Richard J.

===Announcments===

* The first online/DAQ meeting will be next week. Elliott will send out 
an announcement.

==New FDC Geometry options==

Following the DC review, the FDC group came up with some alternative 
designs for the FDC geometry that significantly reduced the amount of 
material. Some changes were made to hdds by Richard to implement these. 
Later, the designs were refined to "option1" and "option2" and 
[[Material specifications for FDC Redesign|documented on the wiki]]. 
David implemented these in hdds and those versions were used for the 
studies presented at the meeting.

Mihajlo showed a couple of plots resulting from simulations done with a 
modified FDC geometry. The one showing the photon detection efficiency 
vs. angle for the original and modified (option 2) displayed some 
unexplainable structure. Namely places where the original geometry had 
better efficiency than the modified geometry which should never happen. 
The second plot showed very little difference between option1 and 
option2 of the new design which was also odd since option2 should have 
had significantly less material in the active region due to the lack of 
foam backing.

David Showed some plots of momentum resolution as a function of momentum 
and angle. These indicated roughly the correct trend that was expected, 
but nothing was shown to indicate the scale of the effect was correct.

It was deicided that Richard should go back and verify the last set of 
changes David made to hdds are correct. Also, we need to check radiation 
length plots to indicate that the changes are as we expect.

==Improvements to Simulation==

Quite a bit of discussion was had on how the output data could be 
modified to (optionally) include additional information.

Currently, special studies that require information not normally found 
outside of gustep.F are done mainly using Ntuples created by turning on 
preprocessor flags and recompiling hdgeant. The normal data output 
includes information about the particles handed to GEANT at the start of 
the event, hit information gathered during the event, and "truth tag" 
information that generally consists of 3D space points and track ids. In 
addition, there is a flag that can be set in the control.in file (TRAJ) 
that will write out detailed information for every step of every tracked 
particle in the simulation. This is useful for only certain types of 
studies since the output files can become quite large.

Suggestions were:
* Add option to insert the "birth" and "death" points of every particle 
in the output stream.
* Add a second flag to determine whether or not the same info for 
secondaries is also added
* Add some info as to the mechanism in which the final state particles 
were created in the generator, possibly including info. on intermediate 
particles not tracked by GEANT.

Since it was not clear to everyone what information is currently 
available in the output datastream, it was suggested that Richard give 
an intro to the simulation at a future software meeting. This would 
likely help new collaborators in particular who are unfamiliar with the 
current simulation package.

==Discussion/Presentation Format==

Elke brought up concerns that we may not be making the best use of our 
time at the software meetings due to a desire to present quick results 
with little supporting evidence to back it up. Some presentations have 
consisted mainly of 1 or 2 plots on the wiki without enough background 
information for a new collaborator to be able to follow the discussion 
easily. She suggested that more time be spent on the presentations with 
less of a sense of urgency to get to the final plot that may not be well 
understood and may also spark long discussions trying to explain what 
may turn out to be a bug in the code.

==Meeting Attendance==

It was suggested that senior collaborators need to make it more of a 
priority for postdocs and students to attend the weekly meetings (like 
the software meeting) since it is a valuable part of their education and 
they are often on the front lines in doing simulation studies.

It was also suggested that the meeting minutes be sent out more 
regularly so people can stay aware of what is being discussed/presented 
even if they are unable to attend. (David said he'd try harder in this 
regard.)

==Action Items==

# Put updated collaboration list in DocDB and commit list to repository 
(Zisis)
# Develop system for incorporating alternative b-fields in simulation  
(Richard and David)
# Look at recent FDC geometry changes (Richard)
# Create an easy way to produce radiation length plots and document it 
(David)
# Review the digitization scheme(s) we have now and figure out how to 
make them more coherent (Beni)

-- 

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  David Lawrence Ph.D.
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