adds Heavy Ion initialization to Pythia [15_0_X]

[michael-pitt]

PR description:

This PR allows initiating the Pythia event generator with ions. The fragment should contain:

generator = cms.EDFilter("Pythia8ConcurrentGeneratorFilter",
   ...
   HeavyIonInitialState = cms.PSet(),
   ...
)

and the user can set up Beams:idA and Beams:idB manually.

PR validation:

Validated with CMSSW_15_0_X

[cmsbuild]

A new Pull Request was created by @michael-pitt for CMSSW_15_0_X.

It involves the following packages:

• GeneratorInterface/Pythia8Interface (generators)

@bbilin, @cmsbuild, @lviliani, @menglu21, @mkirsano can you please review it and eventually sign? Thanks.
@alberto-sanchez, @mkirsano this is something you requested to watch as well.
@antoniovilela, @mandrenguyen, @rappoccio, @sextonkennedy you are the release manager for this.

cms-bot commands are listed here

[cmsbuild]

cms-bot internal usage

[mandrenguyen]

@michael-pitt The usual paradigm is to make a PR to the master release and backport. Is there a reason to do otherwise?

[michael-pitt]

@michael-pitt The usual paradigm is to make a PR to the master release and backport. Is there a reason to do otherwise?

Yes, you are right, I made the PR to the master now (#48414)
I thought it will go faster to 15_0_X this way....

[mandrenguyen]

please test

[cmsbuild]

+1

Size: This PR adds an extra 16KB to repository
Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-4df09b/47126/summary.html
COMMIT: d1c6faa
CMSSW: CMSSW_15_0_X_2025-07-07-2300/el8_amd64_gcc12
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week1/cms-sw/cmssw/48412/47126/install.sh to create a dev area with all the needed externals and cmssw changes.

Comparison Summary

Summary:

• No significant changes to the logs found
• Reco comparison results: 8 differences found in the comparisons
• DQMHistoTests: Total files compared: 50
• DQMHistoTests: Total histograms compared: 4011390
• DQMHistoTests: Total failures: 76
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 4011294
• DQMHistoTests: Total skipped: 20
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 49 files compared)
• Checked 218 log files, 189 edm output root files, 50 DQM output files
• TriggerResults: found differences in 1 / 48 workflows