MergedGenParticleProducer: insert photon mothers for pair-produced leptons

[mseidel42]

PR description:

Rivet uses the following criteria to identify PartonicTops decaying to leptons:

const bool prompt_e = any(descendants, [&](const Particle& p){
  return p.abspid() == PID::ELECTRON && p.isPrompt(_emu_from_prompt_tau) && !p.hasAncestor(PID::PHOTON, false);
});
const bool prompt_mu = any(descendants, [&](const Particle& p){
  return p.abspid() == PID::MUON && p.isPrompt(_emu_from_prompt_tau) && !p.hasAncestor(PID::PHOTON, false);
});

With MiniAOD, low-pt photons going to l+l- are pruned away so that many top decays are wrongly identified as leptonic.
We can fix this by inserting dummy photon mothers for leptons that are not from the hard process or from taus.
As usual, any partonic quantities are inherently unsafe but this should work fine with our usual MadGraph and Powheg MiniAOD samples.
Running from scratch or AOD will not be affected, as well as the ParticleLevelProducer output from MiniAOD (which does not require any lepton mother information).

PR validation:

Validated with events from inclusive TT MiniAod, selecting PartonicTops to dilepton (e/mu) decays:

[cmsbuild]

+code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-38995/31463

• This PR adds an extra 16KB to repository

[cmsbuild]

A new Pull Request was created by @mseidel42 (Markus Seidel) for master.

It involves the following packages:

• GeneratorInterface/RivetInterface (generators)

@SiewYan, @mkirsano, @Saptaparna, @cmsbuild, @alberto-sanchez, @menglu21, @GurpreetSinghChahal can you please review it and eventually sign? Thanks.
@alberto-sanchez, @mkirsano this is something you requested to watch as well.
@perrotta, @dpiparo, @qliphy, @rappoccio you are the release manager for this.

cms-bot commands are listed here

[mseidel42]

Please test 👋

[perrotta]

please test

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-baf975/26878/summary.html
COMMIT: 01667d8
CMSSW: CMSSW_12_5_X_2022-08-17-1100/el8_amd64_gcc10
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week0/cms-sw/cmssw/38995/26878/install.sh to create a dev area with all the needed externals and cmssw changes.

Comparison Summary

There are some workflows for which there are errors in the baseline:
136.9 step 4
The results for the comparisons for these workflows could be incomplete
This means most likely that the IB is having errors in the relvals.The error does NOT come from this pull request

Summary:

• No significant changes to the logs found
• Reco comparison results: 0 differences found in the comparisons
• DQMHistoTests: Total files compared: 51
• DQMHistoTests: Total histograms compared: 3692500
• DQMHistoTests: Total failures: 2
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 3692476
• DQMHistoTests: Total skipped: 22
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 50 files compared)
• Checked 212 log files, 49 edm output root files, 51 DQM output files
• TriggerResults: no differences found

[SiewYan]

+1

Thanks @mseidel42 , everything check out from the code. The validation result looks reasonable.

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next master IBs (tests are also fine). This pull request will now be reviewed by the release team before it's merged. @perrotta, @dpiparo, @rappoccio (and backports should be raised in the release meeting by the corresponding L2)

[perrotta]

please test

• 12 days old tests need to be rerun...

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-baf975/27155/summary.html
COMMIT: 01667d8
CMSSW: CMSSW_12_6_X_2022-08-28-2300/el8_amd64_gcc10
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week0/cms-sw/cmssw/38995/27155/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: 2 differences found in the comparisons
• DQMHistoTests: Total files compared: 51
• DQMHistoTests: Total histograms compared: 3695708
• DQMHistoTests: Total failures: 19
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 3695667
• DQMHistoTests: Total skipped: 22
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 50 files compared)
• Checked 212 log files, 49 edm output root files, 51 DQM output files
• TriggerResults: no differences found

[perrotta]

+1

[makortel]

Looks like this PR is causing segfaults in several workflows, see #39250.

[perrotta]

@mseidel42 @cms-sw/generators-l2 this PR made several workflows (e.g. 10001.0, 10003.0, 10006.0 etc) crash in step 6 in CMSSW_12_6_X_2022-08-30-1100 with a segfault in MergedGenParticleProducer::isLeptonFromPrunedPhoton(), see #39250

Please provide a fix as soon as possible

[Saptaparna]

@mseidel42 : could you please take look at this when possible? Thank you!

[mseidel42]

@mseidel42 : could you please take look at this when possible? Thank you!

Hi Sapta, yes, working on it, see #39250

The problem seems to be limited to electron and muon gun samples.
Maybe it would be worth adding one of those to the test matrix, at least for GEN-related changes, as they seem to be somewhat more fragile than physics samples.