Change from numberOfMatches() to segment number in DisplacedMuonFilterProducer

[24LopezR]

PR description:

This PR intends to fix an unexpected behavior observed when validating the performance of the slimmedDisplacedMuons collection in MiniAOD samples.
The issue consists in a bad filtering of highly displaced muons caused by the definition of muon.numberOfMatches(), which was proved to not be appropriate to effectively select displaced muons when no tracker track is reconstructed.
The fix in this PR proposes to change this variable for another one. Now, the segments of the track are counted through the reco::Track object itself, which yields a more accurate description of the standalone muon track properties.
This issue was reported to and discussed with the MUO POG, a detailed description can be found at:
https://indico.cern.ch/event/1263952/ ("Update on displaced muon collection performance studies").

Muon number expected to increase in muons from the slimmedDisplacedMuons collection which are not .isGlobal() nor .isTracker() in high displaced signals e.g DisplacedSUSY and Cosmics. These muons are not expected to change in prompt signals except for some small fluctuations. Standard muons should not be affected in any way.

The fix has been checked to work properly in cosmics data and H->SS MC signal (higher and lower displacement).

See attached plot for a comparison of muon $d_{xy}$ distribution for a highly displaced H->SS signal (ctau=4000mm) between the old filter (red) and the fix in this PR (blue).

Other authors: @CeliaFernandez

PR validation:

The code changes have passed all standard runTheMatrix test workflows.
No significant increase in size of MiniAOD is expected (tested on ttbar workflow 11834.21)

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:

We would like to have this also backported to 13_0_0.

[cmsbuild]

+code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-41496/35368

• This PR adds an extra 16KB to repository

[cmsbuild]

A new Pull Request was created by @24LopezR (Ruben Lopez) for master.

It involves the following packages:

• PhysicsTools/PatAlgos (xpog, reconstruction)

@swertz, @vlimant, @clacaputo, @cmsbuild, @simonepigazzini, @mandrenguyen can you please review it and eventually sign? Thanks.
@AlexDeMoor, @rappoccio, @gouskos, @jdolen, @JyothsnaKomaragiri, @ahinzmann, @AnnikaStein, @schoef, @emilbols, @jdamgov, @mbluj, @nhanvtran, @gkasieczka, @hatakeyamak, @gpetruc, @azotz, @mariadalfonso, @demuller, @andrzejnovak, @seemasharmafnal, @mmarionncern this is something you requested to watch as well.
@perrotta, @dpiparo, @rappoccio you are the release manager for this.

cms-bot commands are listed here

[mandrenguyen]

please test

[mandrenguyen]

type muon

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-3b626c/32333/summary.html
COMMIT: db1ce80
CMSSW: CMSSW_13_1_X_2023-05-02-2300/el8_amd64_gcc11
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week1/cms-sw/cmssw/41496/32333/install.sh to create a dev area with all the needed externals and cmssw changes.

Comparison Summary

Summary:

• You potentially removed 3 lines from the logs
• Reco comparison results: 466 differences found in the comparisons
• DQMHistoTests: Total files compared: 48
• DQMHistoTests: Total histograms compared: 3460877
• DQMHistoTests: Total failures: 2
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 3460853
• DQMHistoTests: Total skipped: 22
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 47 files compared)
• Checked 207 log files, 159 edm output root files, 48 DQM output files
• TriggerResults: no differences found

[CeliaFernandez]

I had a look at the failed reco comparison results. I would say these are consistent with the changes expected in prompt samples:

Affected muons are slimmedDisplacedMuons with are only displacedStandAloneMuons (StandAloneMuon type in the collection i.e. 00001000). These kind of muons would be the only ones for which the modified lines are executed. See for example in 10224.0 comparison:

The changes in the distributions arise because the number of muons is changing i.e. different muons are filtered w.r.t. reference. The proposed changes should either:

• Increase the number of SA-only displaced muons with numberOfMatches < 2: because they pass the new filter but failed the old one.
• Decrease the number of SA-only displaced muons with numberOfMatches >= 2: because they passed the old filter but now they fail the new one.

This effect can be also checked in workflow 136.793:

[mandrenguyen]

If you moved the minPtSTA check earlier in the code, would it save you from having to calculate the number of segments when the pT threshold condition isn't met?

[24LopezR]

I moved the minPtSTA check to avoid computing nsegments unnecessarily when the condition is not met.

I also checked that the behaviour of the filter remains the same. See attached plot of DSA muon $|d_{xy}|$ variable (both histograms overlap):

[cmsbuild]

+code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-41496/35485

• This PR adds an extra 16KB to repository

[cmsbuild]

Pull request #41496 was updated. @swertz, @vlimant, @clacaputo, @cmsbuild, @simonepigazzini, @mandrenguyen can you please check and sign again.

[mandrenguyen]

please test

[mandrenguyen]

please test
wake up, bot!

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-3b626c/32505/summary.html
COMMIT: e1e435a
CMSSW: CMSSW_13_2_X_2023-05-08-2300/el8_amd64_gcc11
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week0/cms-sw/cmssw/41496/32505/install.sh to create a dev area with all the needed externals and cmssw changes.

Comparison Summary

Summary:

• You potentially removed 2 lines from the logs
• Reco comparison results: 471 differences found in the comparisons
• DQMHistoTests: Total files compared: 48
• DQMHistoTests: Total histograms compared: 3460836
• DQMHistoTests: Total failures: 6
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 3460808
• DQMHistoTests: Total skipped: 22
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 47 files compared)
• Checked 207 log files, 159 edm output root files, 48 DQM output files
• TriggerResults: no differences found

[mandrenguyen]

+reconstruction
Changes consistent with PR description

[simonepigazzini]

+xpog

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

[rappoccio]

+1

While this is perfectly fine for 13_2, we need to discuss the backport to 13_0 since this changes prompt workflows already in production.

[simonepigazzini]

Since prompt is over can we backport this to 13_0? It looks like some EXO analysis could benefit from this fix to the displaced muons collection if this goes into the reMINI campaign for 2022 data/MC.

@rappoccio @antoniovilela @cms-sw/ppd-l2

[24LopezR]

@simonepigazzini Yes, it can be backported to 13_0 (I see there is already a PR for this). Indeed, it would be very benefitial for EXO analyses.