added cut that each tau has at least one pixel hits (for at least one of...

[andrewj314]

... the signal tracks),

in order to reduce increase of jet -> tau fake-rate observed for high pT jets in the Phys14 samples

[cmsbuild]

A new Pull Request was created by @andrewj314 (AJ Johnson) for CMSSW_7_5_X.

added cut that each tau has at least one pixel hits (for at least one of...

It involves the following packages:

RecoTauTag/RecoTau

@cmsbuild, @cvuosalo, @nclopezo, @slava77 can you please review it and eventually sign? Thanks.
@jpavel this is something you requested to watch as well.
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@nclopezo, @ktf you are the release manager for this.
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[slava77]

@cmsbuild please test

@andrewj314 please add a link to slides or other documentation describing the physics impact of this change

[cmsbuild]

The tests are being triggered in jenkins.

[cmsbuild]

+1
Tested at: 895aafd
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-8095/3146/summary.html

[jpavel]

@veelken, can you please provide some slides with the motivation for the fix and its impact?

[veelken]

Hi Pavel,

yes, of course. Arun will present the motivation and the effect on efficiency and fake-rate in the tau ID meeting on Monday.

Cheers,

Christian

[veelken]

Here is the link to the slides:
https://www.dropbox.com/s/l3qslyitmhlt56h/tau_fakerate_09Mar2015.pdf?dl=0

[cvuosalo]

+1

For #8095 895aafd

In Phys14 samples the tau fake rate increased around 5 times at some values of pT compared with 53X. Investigation showed that a cut of at least one pixel hit could eliminate most of this increased fake rate while preserving tau efficiency. This PR implements this new tau cut.

The code change is satisfactory, as are the Jenkins test results. Extended tests against baseline CMSSW_7_5_X_2015-03-05-0200 show no significant differences, except for the expected slight change in tau distributions. There is also a very small reduction (-0.35%, within the statistical uncertainty) in the ECAL converted photon efficiency for photons with ET > 20 GeV that appears in workflow 19.0_SingleGammaPt35+SingleGammaPt35. This tiny efficiency reduction is probably unrelated to this PR. Plots for these two effects are shown below.

Plots showing the decreased tau fake rate and unchanged tau efficiency are linked in this PR thread above.

Minor tau distribution changes (from workflow 25202 ttbar with PU):

Slight converted photon efficiency reduction:

[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]

+1