Disable Not Working leading edge recovery for saturated ECAL RecHits

[emanueledimarco]

• This change disables the leading edge recovery for saturated hits. The method is in place since long time, it works nicely in the simulation, but unfortunately it cannot work on data due to a recently discovered slew-rate limit of the MGPA pre-amplifier that introduces strong non-linearities in the correlation between the 4th sample of the pulse shape and the real energy of the hit.
• More information can be found in the presentation at the last ECAL DPG meeting [1].
• The expected effect of this change is to worsen the resolution of the clusters which include a saturated hit (typically the seed) on simulation, but improve the data-MC agreement in such cases, since the algorithm was giving a pretty random estimate of the energy on data.
• The change should be in principle back-ported to 7.4.X because we would like to have in the RunII Digi-Reco campaign, but we know that there are strong time constraints (discussed at the PPD coord. meeting yesterday [2])
  • in this case the change should be back-ported to 7.3.X sample to make the flat photon gun sample needed for the high ET cluster corrections

@argiro @cerminar @pierinim @ferriff @crovelli @paramatti please also follow this.

[1] https://indico.cern.ch/event/380957/contribution/1/material/slides/0.pdf
[2] http://goo.gl/OViFni

[cmsbuild]

A new Pull Request was created by @emanueledimarco (Emanuele Di Marco) for CMSSW_7_5_X.

Disable Not Working leading edge recovery for saturated ECAL RecHits

It involves the following packages:

RecoLocalCalo/EcalRecProducers

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

@cmsbuild please test

[slava77]

@cmsbuild please test
trying one more time

[cmsbuild]

The tests are being triggered in jenkins.

[emanueledimarco]

@slava77 On this: "Some more details on the physics impact are needed here. (Response changes, fraction of hits affected, data vs mc)"

On the expected changes in the response, I think that the plot is in slide 8 of the presentation linked in the first comment of the pull request [1]. This only regards clusters in a high pT sample where saturation happens (so the effect may be reduced or even invisible in average samples involving typical pT electrons and photons, eg. Z->ee or W->enu).

[1] https://indico.cern.ch/event/380957/contribution/1/material/slides/0.pdf

[slava77]

... we had a reco meeting 5 days ago and this feature wasn't mentioned. Is it so new or was some other reason (Stefano was present and mentioned only integrity error fix relevant to splashes)?

[argiro]

@slava77

On 14 Apr 2015, at 14:49, Slava Krutelyov [email protected] wrote:

... we had a reco meeting 5 days ago and this feature wasn't mentioned. Is it so new or was some other reason (Stefano was present and mentioned only integrity error fix relevant to splashes)?

the Ecal DPG was at the same time as the Reco meeting … that’s why I could not report about the switching off of LE recovery

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[cmsbuild]

+1
Tested at: f043faa
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-8717/2562/summary.html

[slava77]

Differences with respect to the baseline are quite a bit smaller now
(looking here at Run2 setup single-ele 1 TeV )

There is no more bump on the high end of the response spectrum. Values appear to be fairly consistent, with possibly worse resolution, just as expected.

Higher mass or higher pt would probably show more significant change, but I'm not rerunning it at this point, as things appear "normal"

[slava77]

+1

for #8717 cabf698
tested in CMSSW_7_4_0 /test area sign538/
sign off is based on the summary and discussion above.
.. tests were actually done with the 74X version of this PR in #8720 e62dab2

[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