[Halld-offline] HDGeant4 Meeting Minutes, January 29, 2019

[Mark Ito]

Folks,

Please find the minutes here 
<https://halldweb.jlab.org/wiki/index.php/HDGeant4_Meeting,_January_29,_2019#Minutes> 
and below.

   -- Mark

_______________________________


    HDGeant4 Meeting, January 29, 2019, Minutes

Present:

  * *JLab: * Alex Austregesilo, Thomas Britton, Sean Dobbs, Mark Ito
    (chair), Simon Taylor, Beni Zihlmann
  * *UConn: * Richard Jones

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


      Review of minutes from last time

We went over the minutes from January 15 
<https://halldweb.jlab.org/wiki/index.php/HDGeant4_Meeting,_January_15,_2019#Minutes> 
with no new issues raised.


      How to run hdgeant without the DIRC

Richard led us through Richard's email 
<https://mailman.jlab.org/pipermail/halld-offline/2019-January/003504.html>, 
sent earlier today, which addressed two points:

 1. How to run pre-DIRC geometry, when the DIRC is present in the master
    branch of hdds
      * Richard has embellished David Lawrence's mechanism whereby
        hdgeant can generate its HDDS FORTRAN code and corresponding
        libraries on the fly. The details are in his new HOWTO
        <https://halldweb.jlab.org/wiki/index.php/HOWTO_run_hdgeant_simulations_using_ccdb_geometry>.
      * We discussed the utility of having HDDS XML files in the source
        code repository at all. Richard stated that he finds the version
        stored there useful for development.
      * We also discussed the need to built legacy (pre-DIRC) versions
        of HDDS on disk for general use. We thought that that might be
        more trouble than they are worth. [Added in press: second
        thoughts on this have been had by the secretary.]
 2. How to run with the DIRC present, but not suffer the overhead of
    following CKOV photons
      * CKOV turns of Cerenkov photons for all detectors, i. e.,
        globally. Its historical default is CKOV=1 or on. We did not pay
        the computational price since no detector in the default
        geometry had an index of refraction defined, a necessary
        condition for optical photon tracking.
      * Turning off optical photon tracking in the DIRC should speed
        things up by a factor of several.


      Do-over on comparison studies

Thomas presented the first plots from his effort at repeated the studies 
we did when we first starting having HDGeant4 meetings. Find the plots 
here <https://halldweb.jlab.org/wiki/images/9/99/Pim_1_70.pdf>. They are 
all for 1 GeV/c π^− 's at 70 degrees in θ and 0 degrees in φ, and they 
all show the results from HDG3 and HDG4 side-by-side (or top-and-bottom, 
as the case may be). The plots and accompanying discussion appear 
starting at 23:00 in the recording.

A more careful look needs to be taken. More particle settings are to 
come. [Added in press: some ROOT files have been posted by Thomas:

/w/halld-scifs17exp/halld2/home/tbritton/groupMC/G3G4Pure_v2/G3_pim_1_70.root
/w/halld-scifs17exp/halld2/home/tbritton/groupMC/G3G4Pure_v2/G4_pim_1_70.root

File names have the form G[version number]_[particle]_[p GeV]_[theta 
deg].root]


      Note on Upstream Bug Fixes

Richard reported that he has passed the information on bugs he has found 
in Geant4 up to the Geant4 team. He hopes to eventually be able to 
operate without the "G4fixes" part of the HDGeant4 distribution.


      Issues and Pull Requests on GitHub

There weren't any to review.

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