[Backport 10.6.X] Update Pythia Hook for BB4L

[lauridsj]

PR description:

This PR backports #44061 , an update to the Pythia Hook for the BB4L matrix element generator that is needed for the new version of BB4L.

PR validation:

Original PR was tested to produce the same output as the previous version on the old bb4l version, and to produce the same output as a standalone implementation received from the authors (see original PR).

If this PR is a backport please specify the original PR and why you need to backport that PR. If this PR will be backported please specify to which release cycle the backport is meant for:

Backport of #44061 to CMSSW 10_6_X, needed for Run 2 UL MC production.

[cmsbuild]

A new Pull Request was created by @lauridsj for CMSSW_10_6_X.

It involves the following packages:

• GeneratorInterface/Pythia8Interface (generators)

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

cms-bot commands are listed here

[cmsbuild]

cms-bot internal usage

[menglu21]

@cmsbuild please test

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-f3bf10/38220/summary.html
COMMIT: a48d65f
CMSSW: CMSSW_10_6_X_2024-03-10-0000/slc7_amd64_gcc700
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week0/cms-sw/cmssw/44419/38220/install.sh to create a dev area with all the needed externals and cmssw changes.

Comparison Summary

The workflows 1001.0, 1000.0 have different files in step1_dasquery.log than the ones found in the baseline. You may want to check and retrigger the tests if necessary. You can check it in the "files" directory in the results of the comparisons

Summary:

• You potentially added 5 lines to the logs
• Reco comparison results: 0 differences found in the comparisons
• DQMHistoTests: Total files compared: 35
• DQMHistoTests: Total histograms compared: 3215686
• DQMHistoTests: Total failures: 1
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 3215351
• DQMHistoTests: Total skipped: 334
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 34 files compared)
• Checked 144 log files, 103 edm output root files, 35 DQM output files
• TriggerResults: no differences found

[menglu21]

+1

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_10_6_X IBs (tests are also fine) and once validation in the development release cycle CMSSW_14_1_X is complete. This pull request will now be reviewed by the release team before it's merged. @sextonkennedy, @antoniovilela, @rappoccio (and backports should be raised in the release meeting by the corresponding L2)

[rappoccio]

hold

• This looks like a major change so will need to be discussed at the ORP meeting and signed off by PPD.

[cmsbuild]

Pull request has been put on hold by @rappoccio
They need to issue an unhold command to remove the hold state or L1 can unhold it for all

[menglu21]

@jordan-martins @malbouis could you please have a look

[agrohsje]

Hi @malbouis , @jordan-martin, are you ok with merging ?

[malbouis]

Hi @agrohsje , @menglu21 , sorry for the long silence. In principle it should be ok to merge this. I see that the hook is specific to the bb4l, so it doesn't touch Pythia in general, which is good. Then the only other question I had is whether this was tested/validated within cmssw or only privately at the LHE level?
Otherwise, I think it's good to go.

[rappoccio]

unhold

• Discussed already at ORP, will unhold now and merge once PPD is satisfied.

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_10_6_X IBs (tests are also fine) and once validation in the development release cycle CMSSW_14_1_X is complete. This pull request will now be reviewed by the release team before it's merged. @rappoccio, @sextonkennedy, @antoniovilela (and backports should be raised in the release meeting by the corresponding L2)

[rappoccio]

+1

[menglu21]

Hi @agrohsje , @menglu21 , sorry for the long silence. In principle it should be ok to merge this. I see that the hook is specific to the bb4l, so it doesn't touch Pythia in general, which is good. Then the only other question I had is whether this was tested/validated within cmssw or only privately at the LHE level? Otherwise, I think it's good to go.

Hi @malbouis iiuc the LHE is the input of the hook, the comparison should have been done in GEN-level with parton shower and hadronization as mentioned in the initial PR. @lauridsj can comment more.

[lauridsj]

Hi @malbouis @menglu21 , indeed LHE is the input, from which Pythia with the hook then produces GEN events.

I checked, on an event-per-event basis, that this new version of the hook produces the exact same events as the previous one for the same LHE input where applicable, i.e. when called on LHE from the old bb4l version.

For the old version of the hook, I at some point checked that the CMSSW version produces the same distributions as my standalone setup (assuming same Pythia versions & settings).

I also tested that it runs on LHE files from the new bb4l version without crashing, and the resulting distributions seem sensible. Since the new bb4l version is not compatible with the previous version of the hook, no exact comparison of events/distributions for the two hook versions is possible there.

[malbouis]

thanks @lauridsj , @menglu21 and also @agrohsje for replying to the other questions I asked privately.
I see the PR is already merged. It's all good!