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EvtGen tau decays using Pythia
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This task is for implementing tau decays in EvtGen using the Helicity Matrix Element (HME) decay amplitude model in Pythia, which keeps particle spin information. We can then remove all TAUOLA-based code.

Code development should use the tauPythia branch. The decay model is called EvtHmePythia which uses the EvtPythiaEngine, both defined in the EvtGenExternal source and header file directories.

The EvtPythiaEngine::hmeAmplitudes() method needs the initWaves() function in pythia8/include/Pythia8/HelicityMatrixElements.hto be made public (instead of being protected).

Event Timeline

jback triaged this task as Normal priority.Dec 20 2020, 2:39 PM
jback created this task.
jback created this object with visibility "Public (No Login Required)".
jback created this object with edit policy "Restricted Project (Project)".

Example environment setup script, using cvmfs packages:

Example build script, which allows local edits to external packages:

Example run script:

tlatham moved this task from Restricted Project Column to Restricted Project Column on the Restricted Project board.Feb 3 2021, 1:41 PM

For reference, old LHCb JIRA task for tau decays using TAUOLA (which could not add spin info):

There was also some discussion about using general polarisation particle settings in Pythia for tau decays (for special particle decay ordering):