implement correct track breaking if propagation fails #8826
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A new Pull Request was created by @VinInn (Vincenzo Innocente) for CMSSW_7_5_X. implement proper track breaking if propagation fails It involves the following packages: RecoTracker/CkfPattern @cmsbuild, @cvuosalo, @nclopezo, @slava77 can you please review it and eventually sign? Thanks. |
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please remove instead of keeping old development "for posterity"
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The tests are being triggered in jenkins. |
VinInn
changed the title
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| const bool doBackFit = (!doSeedingRegionRebuilding) & (!reverseTrajectories); |
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For clarity, & should be &&, otherwise someone might think bitwise AND is actually needed here instead of logical AND. But this issue doesn't justify changing the PR at this stage -- only fix it if making other changes, too.
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It s intetioanlly BITWISE, because is faster in this particular case.
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+1 A small fix to tracking to reconstruct a few more long tracks. The code changes are satisfactory, as are the Jenkins tests results. Extended tests against baseline CMSSW_7_5_X_2015-04-20-2300 show no problems but do show small changes to many quantities resulting from the tracking changes. DQM plots for workflow 25202.0_TTbar_13+TTbar_13 provide an example of the tracking changes, especially in the region 0.5<|eta|<1.2, as expected. This example shows a 2% reduction in the number of mixed triplet seeds.
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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 |
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+1 |
implement correct track breaking if propagation fails
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There is a pretty visible effect from this change on muon standAloneSET reconstruction (the regular standalone muons are not affected) QCD dijet 3 TeV (mostly punch-through low-pt muons) @jhgoh @battibass @bellan @trocino please follow up. |
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Looking at DQM plots, I see that refittedStandAloneMuons also have changes. So, it's probably something to do with the refit method. |
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To come back to the tracker part of the tracking: regarding the original "Effect is tiny, still visible for 0.5<|eta|<1.2, where more longer tracks are reconstructed." I think a more visible characterization is that more tracks in this area of |eta| with more lost hits are reconstructed; the number of hits isn't changing noticeably enough. As for the seeds, as Vincenzo suggested over email, indeed, there is an increase/migration of the number of tracks in lower iterations (zero to third; fourth ~same; reduction in the fifth and sixth); which explains the reduction in the number of seeds. |
modifications suggested by Ferenc (@sikler) as very visible at low momentum in minimum bias events
The main issue is that previous code in Smoother was "breaking" the track on the "wrong" side
i.e. returning the far part, not the one closest to the vertex.
The new track-shortening algorithm tries to keep the longest possible track preserving the hits closest to the vertex.
Effect is tiny, still visible for 0.5<|eta|<1.2, where more longer tracks are reconstructed.
Small regression expected,
the other two modifications have negligible impact in standard condition.