Fastsim fix ele track ref

[lveldere]

This fixes an issue that caused gsfElectrons with tracker-driven seeds not to be considered as electrons by the particle flow, because a broken link between gsfElectron and recoTrack.

In FastSim, Tracker-driven electron seeds are produced from the track collection before pile-up mixing,
because the algorithm depends on trajectories which are only available before mixing.
Because of this, tracker-driven electrons are linked to the track collection before pile-up mixing.
Particle flow only considers the after-mixing track collection and thus gets confused.

To fix this, A new module, ElectronSeedTrackRefFix, is implemented and inserted in the electron reconstruction sequence. This modules makes a copy of the tracker-driven electron seeds while replacing in each seed,
the reference to the "before mixing" track with a reference to the corresponding "after mixing" track.

[cmsbuild]

A new Pull Request was created by @lveldere for CMSSW_7_5_X.

Fastsim fix ele track ref

It involves the following packages:

FastSimulation/Configuration
FastSimulation/ParticleFlow
FastSimulation/Tracking

@ssekmen, @nclopezo, @lveldere, @civanch, @mdhildreth, @cmsbuild can you please review it and eventually sign? Thanks.
@Martin-Grunewald, @matt-komm this is something you requested to watch as well.
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[lveldere]

please test

[cmsbuild]

The tests are being triggered in jenkins.

[cmsbuild]

+1
Tested at: a28a6cc
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-8143/3198/summary.html

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_5_X IBs unless changes (tests are also fine). This pull request requires discussion in the ORP meeting before it's merged. @davidlange6, @nclopezo, @ktf, @smuzaffar

[davidlange6]

@lveldere - sorry, I had missed the redefinition of trackerDrivenElectronSeeds here before. Is it needed or is it just the same as in the trackerDrivenElectronSeeds_cff?

[lveldere]

@davidlange6

Hi David
trackerDrivenElectronSeedsTmp is the same as trackerDrivenElectronSeeds in trackerDrivenElectronSeeds_cff, except for a different track collection.

[davidlange6]

Right, but what about the redefinition of trackerDrivenElectronSeeds just below the clone?

On Mar 10, 2015, at 11:07 AM, lveldere notifications@github.com wrote:

@davidlange6

Hi David
trackerDrivenElectronSeedsTmp is the same astrackerDrivenElectronSeeds in trackerDrivenElectronSeeds_cff, except for a different track collection.

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Reply to this email directly or view it on GitHub.

[lveldere]

From the description:

"""
A new module, ElectronSeedTrackRefFix, is implemented and inserted in the electron reconstruction sequence. This modules makes a copy of the tracker-driven electron seeds while replacing in each seed,
the reference to the "before mixing" track with a reference to the corresponding "after mixing" track.
"""

With this implemented, PF recognises tracker-driven electrons as electrons.
The copy gets the usual label of the tracker-driven electron seeds,
so that I don't have to make changes further down in the sequences.

[lveldere]

BTW, this is still implemented a bit dirty.

I make the assumption the signal tracks are first in the mixed track collection, which is right.
It would be cleaner to make the track mixer spit out a map between the signal tracks before mixing and the mixed track collection. Then I don't have to make such assumptions. That will be something for the next release.

[davidlange6]

@lveldere - i see now - this is a bit dangerous as we find out from time to time when two previously separate cffs need to be combined. but here it should be ok assuming no consumers of the original producer in fastsim..

With this implemented, PF recognises tracker-driven electrons as electrons.
The copy gets the usual label of the tracker-driven electron seeds,
so that I don't have to make changes further down in the sequences.

[davidlange6]

+1