Raise pT threshold for low pT GSF electron seeds in PbPb era

[mandrenguyen]

It was realized that in the Run 3 configuration lowPtGsfElectronSeeds is one of the most time-consuming parts of the tracking in PbPb events. Electrons in PbPb are only used at pT > 15 GeV, for EW bosons. Reconstruction and identification for low pT elections would be extremely challenging, given the occupancy. In fact, in the pp_on_AA era we had already made the customization: e.toModify(trackerDrivenElectronSeeds, MinPt = 5.0) See: trackerDrivenElectronSeeds_cfi

This PR extends this customization, with the same 5 GeV threshold, to lowPtGsfElectronSeeds Around 5% is saved in the reconstruction time of minimum bias events (tested on 200 events). The AOD size is reduced by less than 0.5%.

The change was tested on wf 159.

[cmsbuild]

+code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-39028/31515

• This PR adds an extra 12KB to repository

[cmsbuild]

A new Pull Request was created by @mandrenguyen (Matthew Nguyen) for master.

It involves the following packages:

• RecoEgamma/EgammaElectronProducers (reconstruction)

@jpata, @cmsbuild, @clacaputo can you please review it and eventually sign? Thanks. @Sam-Harper, @jainshilpi, @valsdav, @rovere, @lgray, @sobhatta, @lecriste, @afiqaize, @wrtabb, @varuns23, @ram1123 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

[jpata]

@cmsbuild please test

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-2e6e72/26778/summary.html COMMIT: 1c364273f8770509fe6af9459b45dd489c6a29fd CMSSW: CMSSW_12_5_X_2022-08-11-2300/el8_amd64_gcc10 User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week1/cms-sw/cmssw/39028/26778/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: 260 differences found in the comparisons
• DQMHistoTests: Total files compared: 51
• DQMHistoTests: Total histograms compared: 3692476
• DQMHistoTests: Total failures: 2
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 3692452
• 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

[jpata]

+reconstruction

• small changes in HI electrons due to changes in the seed threshold (also apparent above 5 GeV due to fakes)

[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, @qliphy, @rappoccio (and backports should be raised in the release meeting by the corresponding L2)

[qliphy]

+1