Realistic vertex smearing for 2015 PbPb MC (81X)

[mandrenguyen]

Update the vertex smearing based on final beamspot fits to the data (taking into account the shift of the pixel detector). The corresponding reco beamspot will be put in a GT and added shortly.
Since the reco beamspot tag is not yet in place, the HI reco relval workflow is not updated to use this vertex smearing. I tested the PR with:

cmsDriver.py MinBias_8TeV_pythia8_TuneCUETP8M1_cff --conditions auto:run2_mc_hi --scenario HeavyIons -n 1 --eventcontent RAWSIM --relval 2000,1 -s GEN,SIM --datatier GEN-SIM --beamspot RealisticHICollision2015 --customise SLHCUpgradeSimulations/Configuration/postLS1Customs.customisePostLS1_HI

There will also be a backport to 75X.

[cmsbuild]

A new Pull Request was created by @mandrenguyen for CMSSW_8_1_X.

It involves the following packages:

Configuration/StandardSequences
IOMC/EventVertexGenerators

@cmsbuild, @civanch, @franzoni, @mdhildreth, @davidlange6 can you please review it and eventually sign? Thanks.
@ghellwig, @makortel, @GiacomoSguazzoni, @rovere, @VinInn, @Martin-Grunewald, @dgulhan this is something you requested to watch as well.
@slava77, @smuzaffar you are the release manager for this.

cms-bot commands are list here #13028

[civanch]

please test

[cmsbuild]

The tests are being triggered in jenkins.
https://cmssdt.cern.ch/jenkins/job/ib-any-integration/14160/console

[cmsbuild]

+1
Tested at: eec613a
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-15224/14160/summary.html

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-15224/14160/summary.html

[civanch]

+1

[civanch]

@mandrenguyen , you removed VtxSmearedUpdatedHICollision2015_cfi, please, confirm that this "Updated" beam-spot is not used anywhere.

[mandrenguyen]

@civanch : Indeed it was never used anywhere. We intended to have an improved guess, but in the end decided to just use the initial predictions. Now that the data is recorded, I think "Realistic" is the appropriate name.