[Halld-offline] HDGeant4 Meeting Minutes, October 18, 2021

[Mark Ito]

Folks,

Please find the minutes here 
<https://halldweb.jlab.org/wiki/index.php/HDGeant4_Meeting,_October_18,_2021#Minutes> 
and below.

   -- Mark

      ________________________________


    HDGeant4 Meeting, October 18, 2021, Minutes

Present: Alex Austregesilo, Sean Dobbs, Mark Ito (chair), Igal Jaegle, 
Richard Jones, Simon Taylor, Beni Zihlmann

There is a recording of this meeting 
<https://bluejeans.com/s/rTLefPvkJ8H/> on the BlueJeans site. Log into 
the BlueJeans site <https://jlab.bluejeans.com> first to gain access 
(use your JLab credentials).


      Review of minutes from the last meeting

We went over the minutes from October 4th 
<https://halldweb.jlab.org/wiki/index.php/HDGeant4_Meeting,_October_4,_2021#Minutes>. 
The issue we discussed, hdgeant4 with updated support packages crashes, 
Issue #198 <https://github.com/JeffersonLab/HDGeant4/issues/198>. Has 
since been solved. It had to do with two fixes for different issues 
related using Qt in visualization. Those fixes were in conflict on nodes 
that had both Qt4 and Qt5 installed.


      Issues on GitHub

We went over the HDGeant4 issues on GitHub 
<https://github.com/JeffersonLab/HDGeant4/issues>.


      Data/MC discrepancy in FCal Matching around Beam Hole #196

  * Alex posted this issue
    <https://github.com/JeffersonLab/HDGeant4/issues/196> last month.
  * Sean mentioned that we have seen effects like this for a long time.
    He has some time to look at it now. He is going to start
    investigating whether there may be accidental contributions in real
    data that are not included by mixing in random triggers in simulated
    events.
  * Igal reminded us that the geometry has shifted. That could be part
    of the problem.
  * Alex has looked at Bethe-Heitler events from Andrew Schick. With
    those, he sees high track matching efficiency near the beam hole.
    This may be due to background events in the sample.
  * Matt Shepherd and Rebecca Barsotti also had some suspicions about
    how we model the background when comparing photon reconstruction
    efficiency in the FCAL between data and simulation.


      Source of Random Trigger Files

Richard wondered whether he needs to continue to serve out random 
trigger files over XROOTD from UConn. The are consuming a lot of space. 
We will ask Thomas Britton about whether JLab can serve as the sole 
source of these files now.


      Package Independence

Mark described work he is doing to build hdgeant4 and halld_sim 
independently from halld_recon by extracting the pieces of halld_recon 
that generate the dependencies. So far he has a system that builds 
against Richard's stand-alone HDDM (removing src/programs/Utilities/hddm 
from halld_recon) and an interface library (replacing src/libraries/HDDM 
from halld_recon) called libhddm at present. To create a stand-alone 
interface library, he has to take a significant number of header files, 
formerly in the detector reconstruction library directories, and ship 
them over the new libhddm. This is so that halld_sim et al. can access 
HDDM-formatted data without having to depend on halld_recon to provide 
that functionality. HDDM is not the only piece responsible for the 
dependence of halld_sim on halld_recon; this is only the first step.

There was a lot of discussion about this plan. One of the main concerns 
was that the header files needed to read HDDM data, e.g., TOF data, 
would be separated from the TOF reconstruction library. Mark argued that 
that is the price one must pay for package independence. There will be 
more discussion at the next software meeting.

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