Support #6265
G4 decays of charm particles is inadequate
0%
Description
When handed a charmed particle (D0, D+, D-, lambda_c+) Geant4 (v4_9_6p02) will propagate the particle until such point it decides that it decays and then produces no decay products.
Under the ART framework used by NOvA and LArSoft, messages of the following form are reported to the log file:
G4Decay::DoIt : decay table not defined for D0
-------- WWWW ------- G4Exception-START -------- WWWW -------
*** G4Exception : DECAY101
issued by : G4Decay::DecayIt
Decay table is not defined
*** This is just a warning message. ***
-------- WWWW -------- G4Exception-END --------- WWWW -------
G4Decay::DoIt : decay table not defined for D+
-------- WWWW ------- G4Exception-START -------- WWWW -------
*** G4Exception : DECAY101
issued by : G4Decay::DecayIt
Decay table is not defined
*** This is just a warning message. ***
-------- WWWW -------- G4Exception-END --------- WWWW -------
This surprises users because of the unphysical behaviour of the sudden loss of energy from the universe.
History
#1 Updated by Robert Hatcher over 5 years ago
Related issue in NOvA's issue tracker: https://cdcvs.fnal.gov/redmine/issues/2852
For NOvA/LArSoft a work-around was implemented such charm particles created by GENIE were decayed by GENIE (via Pythia6) before being handed to Geant4. This was adequate for the immediate needs but is unsatisfying as it leads to displaced vertices without intervening energy loss or scattering.
Note : under Geant4.9.6p02 this lack of a decay table entry does not appear to happen for tau particles; though it did circa 2012-10-19 when reported in NOvA's issue tracker: https://cdcvs.fnal.gov/redmine/issues/3056