[mkFit] propagation to plane in backward fit phase2 and bug fix

[leonardogiannini]

PR description:

The PR improves the initialStep of mkFit currently used by default in phase2.

Propagation to plane is introduced in the backward fit and set as the default in phase2.

Additionally a bug is corrected in the getS function in RecoTracker/MkFitCore/src/PropagationMPlexPlane.cc and the number of step used in the propagation to plane before adding the hit is reduced from 5 to 2, without compromising the physics performance.

The PR should be tested with the new json file from this PR to cms-data: PR18

PR validation:

MTV validation plots can be found here: MTV-bkwdfitPR.

In particular the efficiency, fake and duplicate rates all improve in the initialStep (at build level, but also after selections), see example plots as a function of eta (blue before PR, red after):

At the same time the average number of hits increases by ~0.4.

The choice of number of iterations doens't change the results, so we opted for 2 steps to reduce the timing, see MTV-bkwdfitPR-Niter (initialStep).

The build and fit time for the initialStep are both reduced (MTV-bkwdfitPR-timing), as shown in the plot below:

[cmsbuild]

cms-bot internal usage

[cmsbuild]

-code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-48970/46144

Code check has found code style and quality issues which could be resolved by applying following patch(s)

• code-format:
  https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-48970/46144/code-format.patch
  e.g. curl -k https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-48970/46144/code-format.patch | patch -p1
  You can also run scram build code-format to apply code format directly

[cmsbuild]

+code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-48970/46145

[cmsbuild]

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

It involves the following packages:

• RecoTracker/MkFitCMS (reconstruction)
• RecoTracker/MkFitCore (reconstruction)

@cmsbuild, @jfernan2, @mandrenguyen can you please review it and eventually sign? Thanks.
@GiacomoSguazzoni, @VinInn, @VourMa, @dgulhan, @felicepantaleo, @gpetruc, @makortel, @mmusich, @mtosi, @rovere 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:

• pull_request = Update in phase2 initial step json cms-data/RecoTracker-MkFit#18

[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-fa26f6/48253/summary.html
COMMIT: 48a8598
CMSSW: CMSSW_16_0_X_2025-09-23-1100/el8_amd64_gcc12
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week0/cms-sw/cmssw/48970/48253/install.sh to create a dev area with all the needed externals and cmssw changes.

The following merge commits were also included on top of IB + this PR after doing git cms-merge-topic:

• @iarspider PFAnalyzer.cc: use std::abs #48950
• @KIT-CMS Restructure and comment the tau embedding method #48408

You can see more details here:
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-fa26f6/48253/git-recent-commits.json
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-fa26f6/48253/git-merge-result

Comparison Summary

Summary:

• You potentially removed 72 lines from the logs
• Reco comparison results: 0 differences found in the comparisons
• DQMHistoTests: Total files compared: 53
• DQMHistoTests: Total histograms compared: 4142809
• DQMHistoTests: Total failures: 89737
• DQMHistoTests: Total nulls: 28
• DQMHistoTests: Total successes: 4053024
• DQMHistoTests: Total skipped: 20
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: -0.098 KiB( 52 files compared)
• DQMHistoSizes: changed ( 2024.0010001 ): -0.008 KiB JetMET/SUSYDQM
• DQMHistoSizes: changed ( 2024.0040001 ): -0.090 KiB JetMET/SUSYDQM
• Checked 226 log files, 198 edm output root files, 53 DQM output files
• TriggerResults: no differences found

[jfernan2]

+1

[slava77]

+1

it looks like the bot is still down
#48971 (comment)

[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. @sextonkennedy, @ftenchini, @mandrenguyen (and backports should be raised in the release meeting by the corresponding L2)
Notice This PR was tested with additional Pull Request(s), please also merge them if necessary: cms-data/RecoTracker-MkFit#18