LArSoft Coordination Meeting

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Zoom-only

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At Fermilab:  no in-person presence at the lab for this meeting

 

Erica Snider: Release and project report

  • Wes:  SBN planning to cut a production release this week or next. Are there changes that SBN would care about, eg, optimization of some sort? They would prefer to factorize this change with the on-going push to cut the release?

    • Do not know off hand. Kyle would know, but is away. Suggested checking the release notes.

    • SBN has tested online with art 3.09. Plans to work from production in LArSoft, so anticipates moving to art 3.09 at some point soon.

 

 

Robert Hatcher:  The option for Pythia 8 decays of tau and charm-hadrons in non-Legacy LArG4

  • Follow-up from past talks.

    • Discussed then the inability of Geant4 to properly decay charm and tau

      • If G4 was handed one of these particles, it would get to the decay point, then disappear

      • All sorts of problems ensue from that

    • Dealt with in past by having Genie decay them (via integrated pythia6) before handing them off to G4

      • This produced the decay products, but the tau and charm particles were not tracked, so produced a gap between the production and decay points

      • Nonetheless, was sufficient for some experiments (eg, NOvA) since offset was small, and energy is conserved

      • LArSoft had same solution available

        • Eventually used by DUNE

        • Not by MicroBooNE

        • Unsure about other LArSoft experiments

      • This Genie feature was controlled via GENIE XML configuration file packaged as genie_phyopt UPS product

        • dkcharmtau or dkcharm qualifiers

    • But the gap was a problem, so...

    • G4 started to decay taus, but only at minimal level

      • Not sophisticated. Possibly phase space only?

      • Also had some bugs that messed up momentum calculation in cases

      • So still no solution that simultaneously got the decay and the detector simulation parts right

  • A better solution

    • Let G4 do it's job, and use G4's plug in features to provide alternative for decaying tau and charm

    • Ideally, make it "semi-automatic", or otherwise easy to configure in LArSoft with little coding needed

    • The new solution makes use of G4 extensible physics list factory to supplement regular standard physics lists

      • so "FTFP_BERT " becomes "FTFP_BERT+PY8TAUDK+PY8CHARMDK"

      •  

  • What does PY8TAUDK do?

    • Removes G4's default decay table for taus

    • Register taus to be decayed by Py8TauDecayer, which is a G4VPhysicsConstructor with and interface to pythia8

      • via an instance of G4VExtDecayer : Py8Decayer

      • lives in nug4/AdditionalG4Physics

    •  

    • Similarly, PY8CHARMKD does the same for PDG code signaling charm (or bottom) quarks

    • NOTE: Both also register any other particles that don't already have a decay table in G4 to use pythia8 as well

  • Limitations

    • Works only in non-Legacy LARG4 because it relies ion the extensible physics list factory supplied by G4 (which is not in Legacy LArG4)

    • Also FTFP_BERT+PY8TAUDK == FTFP_BERT+PY8TAUDK+PY8CHARMDK,

      • BUT: FTFP_BERT+PY8CHARMDK != FTFP_BERT+PY8TAUDK+PY8CHARMDK

  • Requires some changes to fcl

    • Need to switch to using the larg4Main module

      • Provided config example for that

    • Need to change the "PhysicsList" configuration to use the new things as noted above

  • Status of this better solution

    • Julia Yarba implemented the interface to Pythia8 in stand-alone G4 app

    • Robert integrated into the factory system so that physics process can be added by configuring the PhysicsList name, and integrated it into nug4 (with a link in larg4)

    • Issues

      • Integrated into NuG4 package (to be avail with art 3.09)

        • added dependence on Pythia8

      • Genie sets tau polarization for RES+DIS, but not QES in it's event record (to be fixed in v3_02)

        • polarization info is in MCTruth in LARSoft event record, and transferred to G4PrimaryParticle

          • nub4/ConvertMCToG4 and larg4/pluginActions/MCTruthEventAction_service.cc

      • Linked to LArG4main to get library loaded at run time

        • nothing needs to be done on user side other tan load the library to make it available; no explicit compile / link time refs

      • Possible to do the same kind of interface for the tauola package.

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