Electron and photon masses are set to zero

[rgoldouz]

Hello,
The electron and photon mass are not saved properly and nanoAOD users reported that many times. It is not related to nanoAOD. The problem is available in miniAOD too.
You can check the printout here
root [6] Events->Scan("Photon_mass:Electron_mass:Muon_mass:Tau_mass")

---

• Row * Instance * Photon_ma * Electron_ * Muon_mass * Tau_mass *

---

•    0 *        0 * 1.348e-06 *           *           * 0.9638671 *
  

•    1 *        0 *         0 *           * 0.1057128 * 0.1395263 *
  

•    2 *        0 * 4.768e-07 *           *           * 0.3725585 *
  

•    2 *        1 * -2.23e-07 *           *           *           *
  

•    3 *        0 * 1.192e-07 *           * 0.1057128 * 0.1395263 *
  

•    3 *        1 * 2.919e-07 *           *           *           *
  

•    4 *        0 * -2.69e-06 *           *           *           *
  

•    4 *        1 *         0 *           *           *           *
  

•    5 *        0 * 6.742e-07 * 0.0024929 *           *           *
  

•    6 *        0 *           * -0.004924 * 0.1057128 * 0.1395263 *
  

•    6 *        1 *           * 0.0061264 * 0.1057128 * 0.1395263 *
  

•    7 *        0 * 6.421e-07 * 0.0085830 *           * 0.1395263 *
  

•    7 *        1 * 1.907e-06 * -0.018432 *           *           *
  

•    7 *        2 * 1.348e-06 *           *           *           *
  

•    8 *        0 *         0 * -0.020462 *           * 1.0068359 *
  

I checked and found that the problem is not from the EGamma code but from TLorentzVector root class. I found that the TLorentz vector is set via pxpypzE for all object candidates. It seems fine but when I tested locally for a particle with pxpypzE=(1,1,1,sqrt(3)) I did not get the mass==0. You can easily reproduce it
root -l
root [1] typedef ROOT::Math::LorentzVector<ROOT::Math::PxPyPzE4D > XYZTLorentzVectorD
root [2] XYZTLorentzVectorD newP4(1,1,1,sqrt(3));
root [3] newP4.M()
(double) -2.1073424e-08

It is because of the precision problem in TLorentz vector and it is recommended to use PxPyPzM to have correct masses for low mass objects.
https://root.cern.ch/doc/master/classROOT_1_1Math_1_1PxPyPzM4D.html

So I set the electron and photon masses by hand to 0 GeV , respectively.

Thanks,
Reza

[cmsbuild]

+code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-36954/28308

• This PR adds an extra 32KB to repository

• There are other open Pull requests which might conflict with changes you have proposed:

  • File RecoEgamma/EgammaElectronAlgos/src/GsfElectronAlgo.cc modified in PR(s): ele/ph mass fix #36889
  • File RecoEgamma/EgammaElectronAlgos/src/RegressionHelper.cc modified in PR(s): ele/ph mass fix #36889
  • File RecoEgamma/EgammaPhotonProducers/src/GEDPhotonProducer.cc modified in PR(s): Implementation of beam halo tagger algorithm for the endcap photons #36901, ele/ph mass fix #36889

[cmsbuild]

A new Pull Request was created by @rgoldouz (Reza Goldouzian) for master.

It involves the following packages:

• RecoEgamma/EgammaElectronAlgos (reconstruction)
• RecoEgamma/EgammaPhotonProducers (reconstruction)

@jpata, @cmsbuild, @clacaputo, @slava77 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 you are the release manager for this.

cms-bot commands are listed here

[jpata]

@cmsbuild please test

[jpata]

thanks @rgoldouz. should the previous PR be closed? If so, please close the old one.

[rgoldouz]

Hi @jpata

Done.

Thanks,
Reza

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-5d6736/22402/summary.html
COMMIT: 47f12d9
CMSSW: CMSSW_12_3_X_2022-02-13-2300/slc7_amd64_gcc10
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week0/cms-sw/cmssw/36954/22402/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: 226 differences found in the comparisons
• DQMHistoTests: Total files compared: 46
• DQMHistoTests: Total histograms compared: 3764435
• DQMHistoTests: Total failures: 267
• DQMHistoTests: Total nulls: 1
• DQMHistoTests: Total successes: 3764145
• DQMHistoTests: Total skipped: 22
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.004 KiB( 45 files compared)
• DQMHistoSizes: changed ( 312.0 ): 0.004 KiB MessageLogger/Warnings
• Checked 193 log files, 42 edm output root files, 46 DQM output files
• TriggerResults: no differences found

[jpata]

I'm surprised to see differences in MET corrections and uncertainties:
https://cmssdt.cern.ch/SDT/jenkins-artifacts/baseLineComparisons/CMSSW_12_3_X_2022-02-13-2300+5d6736/48363/validateJR/all_mini_OldVSNew_RunDoubleEG2017Cwf136p793/

https://cmssdt.cern.ch/SDT/jenkins-artifacts/baseLineComparisons/CMSSW_12_3_X_2022-02-13-2300+5d6736/48363/validateJR/all_mini_OldVSNew_RunDoubleEG2017Cwf136p793/all_mini_OldVSNew_RunDoubleEG2017Cwf136p793c_patMETs_slimmedMETs__reRECO_obj_0__corrections__1__dpx58.png

maybe @michaelwassmer has some idea why this can happen by changing the electron mass?

[jpata]

just a kind ping on this. it may be useful for JME experts to weigh in if the change is expected.

[michaelwassmer]

Sorry for not answering earlier. This week I'm already busy with a lot of other things, so I try to have a look at it next week.

[jpata]

@cmsbuild please test

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-5d6736/22733/summary.html
COMMIT: 47f12d9
CMSSW: CMSSW_12_3_X_2022-03-01-1100/slc7_amd64_gcc10
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week0/cms-sw/cmssw/36954/22733/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: 246 differences found in the comparisons
• DQMHistoTests: Total files compared: 49
• DQMHistoTests: Total histograms compared: 4000857
• DQMHistoTests: Total failures: 275
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 4000560
• DQMHistoTests: Total skipped: 22
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 48 files compared)
• Checked 204 log files, 45 edm output root files, 49 DQM output files
• TriggerResults: no differences found

[jpata]

what I don't understand here is why only the MET corrections differ, and not the MET itself, if the electron 4-vector changes.

[rgoldouz]

@rgoldouz Please edit the PR title and description more meaningful, probably following your original PR #36889 For example, current PR title is "electron mass set to zero", but you set also photon mass to zero.

Hi @qliphy , Done. Thanks.

[perrotta]

please test

[cmsbuild]

+code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-36954/28708

• This PR adds an extra 36KB to repository

[cmsbuild]

Pull request #36954 was updated. @jpata, @clacaputo, @slava77 can you please check and sign again.

[perrotta]

@rgoldouz Please edit the PR title and description more meaningful, probably following your original PR #36889 For example, current PR title is "electron mass set to zero", but you set also photon mass to zero.

Hi @qliphy , Done. Thanks.

Uhm, @rgoldouz what you did instead was to add two more (empty) commits with the title that @qliphy suggested for this PR. And this by the way forced us to relaunch the tests.
Assuming that the title that you assigned for the additional commits is the one that you wanted to give to the PR, I modified the title of this PR accordingly. Please update it (by clicking the "Edit" button on the right side of the title in this github thread) if you want to adjust it further.

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-5d6736/22889/summary.html
COMMIT: 8c39182
CMSSW: CMSSW_12_3_X_2022-03-05-1100/slc7_amd64_gcc10
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week0/cms-sw/cmssw/36954/22889/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: 247 differences found in the comparisons
• DQMHistoTests: Total files compared: 49
• DQMHistoTests: Total histograms compared: 3987741
• DQMHistoTests: Total failures: 274
• DQMHistoTests: Total nulls: 1
• DQMHistoTests: Total successes: 3987444
• DQMHistoTests: Total skipped: 22
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.004 KiB( 48 files compared)
• DQMHistoSizes: changed ( 312.0 ): 0.004 KiB MessageLogger/Warnings
• Checked 204 log files, 45 edm output root files, 49 DQM output files
• TriggerResults: no differences found

[jpata]

+reconstruction

• no relevant changes since Electron and photon masses are set to zero #36954 (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. @perrotta, @dpiparo, @qliphy (and backports should be raised in the release meeting by the corresponding L2)

[qliphy]

+1

[swagata87]

type egamma

it's rather hard to find out later on unless its tagged as egamma... so...