[Halld-offline] HDGeant4 Meeting Minutes, January 28, 2020

[Mark Ito]

Folks,

These minutes are from Tuesday, a week ago. Please find them here 
<https://halldweb.jlab.org/wiki/index.php/HDGeant4_Meeting,_January_28,_2020#Minutes> 
and below.

   -- Mark


  HDGeant4 Meeting, January 28, 2020, Minutes

Present:

  * *CMU: * Naomi Jarvis
  * *FSU: * Sean Dobbs
  * *JLab: * Alex Austregesilo, Colin Gleason, Mark Ito (chair), Simon
    Taylor, Beni Zihlmann
  * *UConn: * Richard Jones, James McIntyre
  * *W&M: * Justin Stevens

There is a recording of this meeting <https://bluejeans.com/s/1M0qK/> on 
the BlueJeans site. Use your JLab credentials to get access.


      Review of minutes from the last Meeting

We went over the minutes from January 14 
<https://halldweb.jlab.org/wiki/index.php/HDGeant4_Meeting,_January_14,_2020#Minutes>. 



        Calorimeter timing mismatch between g3 and g4

This is Issue #93 <https://github.com/JeffersonLab/HDGeant4/issues/93>.

Colin has extended his work on this issue, widening the timing cuts as 
Alex did for his ρ analysis. He sees indeed that G3 and G4 both have 
significant tails in BCAL timing for π^− s, with the tail bigger for G3.

When looking at acceptance for the full reaction (pγ→ηπ^− Δ^++ ) as 
function of Gottfried-Jackson angle the differing shapes remain, except 
the G4 efficiency drops in level from about 4% to 2.5% while retaining 
its overall shape. Alex saw a similar effect in the ρs until he fixed 
the bug whereby the choice of RF bunch was defeated by a lack of 
agreement among multiple tracks inside the wide timing window. Colin 
will go back and repeat his study with the current master branch of 
halld_recon.


      Systematic studies of Geant3/Geant4 differences

Alex presented Igal's work on Monte Carlo studies of γp→ωp and ω→π^+ π^− 
π^0 ;. He compared simulations with:

  * G3 vs. G4
  * no accidental background events, background from Richard's MC beam
    background generator, and random trigger events mixed in
  * run 30496 vs. run 30730

for a total of twelve different sets of conditions. He showed a variety 
of different comparisons among these conditions including single 
particle distributions, invariant mass distributions and occupancy plots 
for the FCAL. Please see his slides for the rich variety of comparisons 
available 
<https://halldweb.jlab.org/DocDB/0043/004314/001/primexd-igal-jaegle-27012020.pdf>. 
 From Igal's last slide, here are his conclusions:

  * Low-level systematic comparisons between different Geant versions
    and runs, and with and without background combined: Geant3 and
    Geant4 show clear difference without any backgrounds included
      o More photons/hits are produced in Geant4 (observed mostly in
        FCAL due possibly to ω physics/decay)
  * All the other differences listed below are happening outside of
    Geant Without backgrounds (but also with backgrounds)
      o Calibration tables although identical are applied differently to
        Geant3 and Geant4 simulations possibly because they are not
        applied at the same variable(s)?
  * Combination of background/noise to simulation produces different
    outcome for Geant3 and Geant4 simulations
  * Combination of background/noise to Geant3 simulations are consistent
    and evenly distributed => seems correct
  * Combination of background/noise to Geant4 simulations are
    inconsistent and not evenly distributed
      o Background/noise mostly located at the edge and
      o Creates spikes
      o => seems buggy
  * As the same code is used to combine the background/noise to both
    simulation version, it probably means it is not using the same
    variable(s)?


      Collaboration Meeting

We need to make some sort of report out of this group on work since the 
last collaboration meeting. Mark and Sean will get together and discuss 
options. Stay tuned.

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  * This page was last modified on 4 February 2020, at 14:38.

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