auto detect first vertex with Higgs in children list

[yihui-lai]

PR description:

The current HTXS production-mode identification relies on inspecting GenEvent::vertices()[0] to determine the Higgs boson’s production topology. However, for certain MG5_aMC@NLO FxFx samples—such as TTH-Hto2G_Par-M-125_TuneCP5_13p6TeV_amcatnloFXFX-pythia8—the Higgs does not appear among the children of vertices()[0].

As a result, the HTXS Rivet module fails to assign a valid Higgs production mode, which propagates to a failure in HTXS categorization during MiniAOD→NanoAOD production. This PR updates the logic to automatically identify the first GenVertex that contains a Higgs boson among its outgoing particles, rather than assuming it is located at vertices()[0].

PR validation:

The updated logic was validated by running MiniAOD → NanoAOD workflows on both:

• MG5_aMC@NLO FxFx samples (e.g. problematic TTH FxFx datasets)
• POWHEG samples

In all tested samples, the HTXS production mode and category are now correctly assigned.

@mseidel42

[cmsbuild]

A new Pull Request was created by @yihui-lai for CMSSW_15_0_2_patchX.

It involves the following packages:

• GeneratorInterface/RivetInterface (generators)

@cmsbuild, @lviliani, @mkirsano, @sensrcn, @theofil can you please review it and eventually sign? Thanks.
@alberto-sanchez, @mkirsano this is something you requested to watch as well.
@ftenchini, @mandrenguyen, @sextonkennedy you are the release manager for this.
Note that this branch is designed for requested bug fixes specific to the CMSSW_15_0_2 release.
If you wish to make a pull request for the CMSSW_15_0_X release cycle, please use the CMSSW_15_0_X branch instead

cms-bot commands are listed here

[cmsbuild]

cms-bot internal usage

[lviliani]

please test

[cmsbuild]

+1

Size: This PR adds an extra 24KB to repository
Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-f64349/49922/summary.html
COMMIT: de23188
CMSSW: CMSSW_15_0_X_2025-12-07-0000/el8_amd64_gcc12
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week1/cms-sw/cmssw/49611/49922/install.sh to create a dev area with all the needed externals and cmssw changes.

Comparison Summary

Summary:

• You potentially removed 1 lines from the logs
• Reco comparison results: 9 differences found in the comparisons
• DQMHistoTests: Total files compared: 50
• DQMHistoTests: Total histograms compared: 4031514
• DQMHistoTests: Total failures: 9
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 4031485
• 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: no differences found