LST: T5-T5 Duplicate Merging

[GNiendorf]

PR description:

This PR introduces a duplicate merging strategy for Line Segment Tracking (LST) that extends track candidates by recovering hits from duplicate T5 tracklets that were previously discarded. The algorithm iterates over T5s to identify duplicates eligible for merging, requiring that they pass a set of selections and originate from different layers. A new kernel, ExtendTrackCandidatesFromDupT5, merges hits from the highest-scoring duplicates into LST track candidates. About 70% of LST T5 and pT5 track candidates gain additional hits, improving pT resolution and increasing track candidate length with negligible impact on timing.

More info: LST Duplicate Merging.pdf

cc. @slava77

[cmsbuild]

cms-bot internal usage

[cmsbuild]

+code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-49623/47161

[cmsbuild]

A new Pull Request was created by @GNiendorf for master.

It involves the following packages:

• DataFormats/Common (core)
• RecoTracker/LST (reconstruction)
• RecoTracker/LSTCore (reconstruction)

@Dr15Jones, @Moanwar, @cmsbuild, @jfernan2, @makortel, @mandrenguyen, @smuzaffar, @srimanob can you please review it and eventually sign? Thanks.
@GiacomoSguazzoni, @VinInn, @VourMa, @dgulhan, @elusian, @felicepantaleo, @gpetruc, @makortel, @missirol, @mmasciov, @mmusich, @mtosi, @rovere, @wddgit this is something you requested to watch as well.
@ftenchini, @mandrenguyen, @sextonkennedy you are the release manager for this.

cms-bot commands are listed here

[slava77]

test parameters:

• enable = hlt_p2_integration, hlt_p2_timing
• workflows = ph2_hlt

[slava77]

@cmsbuild 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-80ead6/49964/summary.html
COMMIT: 4cb70db
CMSSW: CMSSW_16_0_X_2025-12-13-1100/el8_amd64_gcc13
Additional Tests: HLT_P2_INTEGRATION,HLT_P2_TIMING
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week1/cms-sw/cmssw/49623/49964/install.sh to create a dev area with all the needed externals and cmssw changes.

HLT P2 Timing: chart

Comparison Summary

Summary:

• You potentially added 3 lines to the logs
• ROOTFileChecks: Some differences in event products or their sizes found
• Reco comparison results: 6 differences found in the comparisons
• Reco comparison had 4 failed jobs
• DQMHistoTests: Total files compared: 73
• DQMHistoTests: Total histograms compared: 5017231
• DQMHistoTests: Total failures: 9535
• DQMHistoTests: Total nulls: 3
• DQMHistoTests: Total successes: 5007673
• DQMHistoTests: Total skipped: 20
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 72 files compared)
• Checked 295 log files, 253 edm output root files, 73 DQM output files
• TriggerResults: found differences in 4 / 71 workflows

[jfernan2]

+1

[makortel]

+core

[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. @ftenchini, @mandrenguyen, @sextonkennedy (and backports should be raised in the release meeting by the corresponding L2)