Consider charge conjugation in decay products in PythiaFilterMultiAncestor

[rmanzoni]

PR description:

In this PR we address a design problem of PythiaFilterMultiAncestor.cc, where charge conjugation is implicitly assumed by default for the particle under investigation
https://github.com/cms-sw/cmssw/blob/master/GeneratorInterface/GenFilters/plugins/PythiaFilterMultiAncestor.cc#L147
for its ancestor
https://github.com/cms-sw/cmssw/blob/master/GeneratorInterface/GenFilters/plugins/PythiaFilterMultiAncestor.cc#L122
, but it is not for its daughters.
https://github.com/cms-sw/cmssw/blob/master/GeneratorInterface/GenFilters/plugins/PythiaFilterMultiAncestor.cc#L190

The problem was noticed in some private tests and should not affect any samples produced so far using this filter (which in fact is just a limited number of samples for a specific analysis and they are not affected because in that case it was based on a Jpsi->mumu decay).
However, a backport to 10_6 (and 11?) would be good to avoid having production releases where the filter behaves in an unintended way.

PR validation:

The problem was noticed when using the filter to enforce D0->K-pi+ decay.

D0ToKpiFromDstFilter = cms.EDFilter(
    "PythiaFilterMultiAncestor",
    DaughterIDs     = cms.untracked.vint32 ( -321,   211), # K-, pion+ 
    DaughterMaxEtas = cms.untracked.vdouble( 1.e9,  1.e9),
    DaughterMaxPts  = cms.untracked.vdouble( 1.e9,  1.e9),
    DaughterMinEtas = cms.untracked.vdouble(-1.e9, -1.e9),
    DaughterMinPts  = cms.untracked.vdouble(-1.0 , -1.0 ),
    MaxEta          = cms.untracked.double ( 99.0),
    MinEta          = cms.untracked.double (-99.0),
    MinPt           = cms.untracked.double (-1.0),
    MotherIDs       = cms.untracked.vint32 (413), # D*+
    ParticleID      = cms.untracked.int32  (421) # D0
)

Only one charge combination was present, but not the cc. The fix proposed here implements the correct behaviour.

[cmsbuild]

-code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-33491/22221

• This PR adds an extra 16KB to repository

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-33491/22221/code-format.patch
  e.g. curl https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-33491/22221/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-33491/22224

• This PR adds an extra 16KB to repository

[cmsbuild]

A new Pull Request was created by @rmanzoni (Riccardo Manzoni) for master.

It involves the following packages:

GeneratorInterface/GenFilters

@SiewYan, @mkirsano, @cmsbuild, @GurpreetSinghChahal, @agrohsje, @alberto-sanchez can you please review it and eventually sign? Thanks.
@alberto-sanchez, @mkirsano this is something you requested to watch as well.
@silviodonato, @dpiparo, @qliphy you are the release manager for this.

cms-bot commands are listed here

[SiewYan]

please test

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-795d33/14550/summary.html
COMMIT: 3f2f8ce
CMSSW: CMSSW_12_0_X_2021-04-23-1100/slc7_amd64_gcc900
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week1/cms-sw/cmssw/33491/14550/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: 4 differences found in the comparisons
• DQMHistoTests: Total files compared: 38
• DQMHistoTests: Total histograms compared: 2877046
• DQMHistoTests: Total failures: 7
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 2877017
• DQMHistoTests: Total skipped: 22
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 37 files compared)
• Checked 160 log files, 37 edm output root files, 38 DQM output files
• TriggerResults: no differences found

[SiewYan]

Looks good to me!

[SiewYan]

+1

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

[qliphy]

+1