Add softdrop normalization parameter

[jdolen]

The soft drop groomer requires three parameters:
https://github.com/cms-externals/fastjet-contrib/blob/master/RecursiveTools/SoftDrop.hh
/// \param beta the value of the beta parameter
/// \param symmetry_cut the value of the cut on the symmetry measure (zcut)
/// \param R0 the angular distance normalisation [1 by default]

By default R0 is set to 1, but ideally it should be set to the jet radius. See equation 1 here:
http://arxiv.org/pdf/1402.2657v2.pdf

The initial CMSSW implementation only included beta and zcut. I've added the R0 parameter and set it to the jet radius for ak8PFJetsCHSSoftDrop, ak4PFJetsSoftDrop, and ak5PFJetsSoftDrop.

[cmsbuild]

A new Pull Request was created by @jdolen (James Dolen) for CMSSW_7_4_X.

Add softdrop normalization parameter

It involves the following packages:

RecoJets/Configuration
RecoJets/JetProducers

@cmsbuild, @cvuosalo, @nclopezo, @slava77 can you please review it and eventually sign? Thanks.
@rappoccio, @yslai, @TaiSakuma, @ahinzmann, @nhanvtran, @schoef, @mariadalfonso this is something you requested to watch as well.
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[cvuosalo]

@cmsbuild please test

[cmsbuild]

The tests are being triggered in jenkins.

[cmsbuild]

+1
Tested at: b816f31
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-7978/2962/summary.html

[cvuosalo]

Starting extended tests...

[cvuosalo]

+1

For #7978 b816f31

An angular distance normalization parameter (R0) to the soft drop jet groomer was changed from its default value to the jet radius for three soft drop jet collections.

The code change is satisfactory. The Jenkins tests are OK and show no significant differences. Extended tests against baseline CMSSW_7_4_X_2015-02-25-1400 for workflows 313.0_QCD_Pt_3000, 1338.0_QCD_FlatPt, 202.0_TTbar, 25202.0_TTbar, and 38.0_QCD_FlatPt show no significant differences.

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_4_X IBs unless changes (tests are also fine). This pull request requires discussion in the ORP meeting before it's merged. @davidlange6, @Degano, @ktf, @smuzaffar

[davidlange6]

+1